Bug 27212

Summary: Warning kmemcheck: Caught 64-bit read from uninitialized memory in netlink_broadcast_filtered
Product: Other Reporter: Christian Casteyde (casteyde.christian)
Component: OtherAssignee: other_other
Status: CLOSED UNREPRODUCIBLE    
Severity: normal CC: florian
Priority: P1    
Hardware: All   
OS: Linux   
Kernel Version: 2.6.38-rc1 Subsystem:
Regression: Yes Bisected commit-id:

Description Christian Casteyde 2011-01-20 20:07:32 UTC
Athlon 64 X2 3000 in 64bits
Slackware64 13.1
Kernel compiled with kmemcheck and other debug options

At boot I got the following warning:

PCI: Using ACPI for IRQ routing
PCI: pci_cache_line_size set to 64 bytes
pci 0000:00:00.0: address space collision: [mem 0xe0000000-0xefffffff pref] conflicts with GART [mem 0x
e0000000-0xefffffff]
reserve RAM buffer: 000000000009fc00 - 000000000009ffff 
reserve RAM buffer: 000000003ffb0000 - 000000003fffffff
WARNING: kmemcheck: Caught 64-bit read from uninitialized memory (ffff88003e170eb0)
0000000000000000010000000000000000000000000000000000000000000000
 i i i i i i i i i i i i u u u u u u u u u u u u u u u u u u u u
                                 ^

Pid: 1, comm: swapper Not tainted 2.6.38-rc1 #2 K8 Combo-Z/K8 Combo-Z
RIP: 0010:[<ffffffff8127ad72>]  [<ffffffff8127ad72>] memmove+0x122/0x1a0
RSP: 0018:ffff88003e0b3c60  EFLAGS: 00010202
RAX: ffff88003e170080 RBX: ffff88003e27b500 RCX: 0000000000000020
RDX: 0000000000000018 RSI: ffff88003e170ea0 RDI: ffff88003e1700a0
RBP: ffff88003e0b3c60 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000080 R14: 0000000000000000 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff88003fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: ffff88003e018abc CR3: 0000000001a1c000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7: 0000000000000400
 [<ffffffff814741c2>] pskb_expand_head+0xc2/0x2a0
 [<ffffffff81498fa7>] netlink_broadcast_filtered+0xa7/0x4a0
 [<ffffffff814993b8>] netlink_broadcast+0x18/0x20
 [<ffffffff8149b884>] genlmsg_mcast+0x144/0x180
 [<ffffffff8149bc4a>] genl_ctrl_event+0xca/0x450
 [<ffffffff8149c75d>] genl_register_mc_group+0x10d/0x2a0
 [<ffffffff81ad9da4>] genl_init+0x6c/0x84
 [<ffffffff810001de>] do_one_initcall+0x3e/0x170
 [<ffffffff81aae6ea>] kernel_init+0x197/0x21b
 [<ffffffff81003254>] kernel_thread_helper+0x4/0x10
 [<ffffffffffffffff>] 0xffffffffffffffff
pnp: PnP ACPI init
ACPI: bus type pnp registered
pnp 00:00: [bus 00-ff]
pnp 00:00: [io  0x0cf8-0x0cff]

This is specific to 2.6.38-rc1.
Comment 1 Andrew Morton 2011-01-20 20:26:55 UTC
(switched to email.  Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Thu, 20 Jan 2011 20:08:32 GMT
bugzilla-daemon@bugzilla.kernel.org wrote:

> https://bugzilla.kernel.org/show_bug.cgi?id=27212
> 
>            Summary: Warning kmemcheck: Caught 64-bit read from
>                     uninitialized memory in netlink_broadcast_filtered
>            Product: Other
>            Version: 2.5
>     Kernel Version: 2.6.38-rc1
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: Other
>         AssignedTo: other_other@kernel-bugs.osdl.org
>         ReportedBy: casteyde.christian@free.fr
>         Regression: Yes
> 
> 
> Athlon 64 X2 3000 in 64bits
> Slackware64 13.1
> Kernel compiled with kmemcheck and other debug options
> 
> At boot I got the following warning:
> 
> PCI: Using ACPI for IRQ routing
> PCI: pci_cache_line_size set to 64 bytes
> pci 0000:00:00.0: address space collision: [mem 0xe0000000-0xefffffff pref]
> conflicts with GART [mem 0x
> e0000000-0xefffffff]
> reserve RAM buffer: 000000000009fc00 - 000000000009ffff 
> reserve RAM buffer: 000000003ffb0000 - 000000003fffffff
> WARNING: kmemcheck: Caught 64-bit read from uninitialized memory
> (ffff88003e170eb0)
> 0000000000000000010000000000000000000000000000000000000000000000
>  i i i i i i i i i i i i u u u u u u u u u u u u u u u u u u u u
>                                  ^
> 
> Pid: 1, comm: swapper Not tainted 2.6.38-rc1 #2 K8 Combo-Z/K8 Combo-Z
> RIP: 0010:[<ffffffff8127ad72>]  [<ffffffff8127ad72>] memmove+0x122/0x1a0
> RSP: 0018:ffff88003e0b3c60  EFLAGS: 00010202
> RAX: ffff88003e170080 RBX: ffff88003e27b500 RCX: 0000000000000020
> RDX: 0000000000000018 RSI: ffff88003e170ea0 RDI: ffff88003e1700a0
> RBP: ffff88003e0b3c60 R08: 0000000000000001 R09: 0000000000000001
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000080 R14: 0000000000000000 R15: 0000000000000001
> FS:  0000000000000000(0000) GS:ffff88003fc00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: ffff88003e018abc CR3: 0000000001a1c000 CR4: 00000000000006f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7: 0000000000000400
>  [<ffffffff814741c2>] pskb_expand_head+0xc2/0x2a0
>  [<ffffffff81498fa7>] netlink_broadcast_filtered+0xa7/0x4a0
>  [<ffffffff814993b8>] netlink_broadcast+0x18/0x20
>  [<ffffffff8149b884>] genlmsg_mcast+0x144/0x180
>  [<ffffffff8149bc4a>] genl_ctrl_event+0xca/0x450
>  [<ffffffff8149c75d>] genl_register_mc_group+0x10d/0x2a0
>  [<ffffffff81ad9da4>] genl_init+0x6c/0x84
>  [<ffffffff810001de>] do_one_initcall+0x3e/0x170
>  [<ffffffff81aae6ea>] kernel_init+0x197/0x21b
>  [<ffffffff81003254>] kernel_thread_helper+0x4/0x10
>  [<ffffffffffffffff>] 0xffffffffffffffff
> pnp: PnP ACPI init
> ACPI: bus type pnp registered
> pnp 00:00: [bus 00-ff]
> pnp 00:00: [io  0x0cf8-0x0cff]
> 
> This is specific to 2.6.38-rc1.
>
Comment 2 Eric Dumazet 2011-01-20 20:42:03 UTC
Le jeudi 20 janvier 2011 à 12:25 -0800, Andrew Morton a écrit :
> (switched to email.  Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
> 
> On Thu, 20 Jan 2011 20:08:32 GMT
> bugzilla-daemon@bugzilla.kernel.org wrote:
> 
> > https://bugzilla.kernel.org/show_bug.cgi?id=27212
> > 
> >            Summary: Warning kmemcheck: Caught 64-bit read from
> >                     uninitialized memory in netlink_broadcast_filtered
> >            Product: Other
> >            Version: 2.5
> >     Kernel Version: 2.6.38-rc1
> >           Platform: All
> >         OS/Version: Linux
> >               Tree: Mainline
> >             Status: NEW
> >           Severity: normal
> >           Priority: P1
> >          Component: Other
> >         AssignedTo: other_other@kernel-bugs.osdl.org
> >         ReportedBy: casteyde.christian@free.fr
> >         Regression: Yes
> > 
> > 
> > Athlon 64 X2 3000 in 64bits
> > Slackware64 13.1
> > Kernel compiled with kmemcheck and other debug options
> > 
> > At boot I got the following warning:
> > 
> > PCI: Using ACPI for IRQ routing
> > PCI: pci_cache_line_size set to 64 bytes
> > pci 0000:00:00.0: address space collision: [mem 0xe0000000-0xefffffff pref]
> > conflicts with GART [mem 0x
> > e0000000-0xefffffff]
> > reserve RAM buffer: 000000000009fc00 - 000000000009ffff 
> > reserve RAM buffer: 000000003ffb0000 - 000000003fffffff
> > WARNING: kmemcheck: Caught 64-bit read from uninitialized memory
> > (ffff88003e170eb0)
> > 0000000000000000010000000000000000000000000000000000000000000000
> >  i i i i i i i i i i i i u u u u u u u u u u u u u u u u u u u u
> >                                  ^
> > 
> > Pid: 1, comm: swapper Not tainted 2.6.38-rc1 #2 K8 Combo-Z/K8 Combo-Z
> > RIP: 0010:[<ffffffff8127ad72>]  [<ffffffff8127ad72>] memmove+0x122/0x1a0
> > RSP: 0018:ffff88003e0b3c60  EFLAGS: 00010202
> > RAX: ffff88003e170080 RBX: ffff88003e27b500 RCX: 0000000000000020
> > RDX: 0000000000000018 RSI: ffff88003e170ea0 RDI: ffff88003e1700a0
> > RBP: ffff88003e0b3c60 R08: 0000000000000001 R09: 0000000000000001
> > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> > R13: 0000000000000080 R14: 0000000000000000 R15: 0000000000000001
> > FS:  0000000000000000(0000) GS:ffff88003fc00000(0000)
> knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> > CR2: ffff88003e018abc CR3: 0000000001a1c000 CR4: 00000000000006f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7: 0000000000000400
> >  [<ffffffff814741c2>] pskb_expand_head+0xc2/0x2a0
> >  [<ffffffff81498fa7>] netlink_broadcast_filtered+0xa7/0x4a0
> >  [<ffffffff814993b8>] netlink_broadcast+0x18/0x20
> >  [<ffffffff8149b884>] genlmsg_mcast+0x144/0x180
> >  [<ffffffff8149bc4a>] genl_ctrl_event+0xca/0x450
> >  [<ffffffff8149c75d>] genl_register_mc_group+0x10d/0x2a0
> >  [<ffffffff81ad9da4>] genl_init+0x6c/0x84
> >  [<ffffffff810001de>] do_one_initcall+0x3e/0x170
> >  [<ffffffff81aae6ea>] kernel_init+0x197/0x21b
> >  [<ffffffff81003254>] kernel_thread_helper+0x4/0x10
> >  [<ffffffffffffffff>] 0xffffffffffffffff
> > pnp: PnP ACPI init
> > ACPI: bus type pnp registered
> > pnp 00:00: [bus 00-ff]
> > pnp 00:00: [io  0x0cf8-0x0cff]
> > 
> > This is specific to 2.6.38-rc1.
> > 
> 

Likely a false positive after commit ca44ac38
(net: don't reallocate skb->head unless the current one hasn't the
needed extra size or is shared)

ksize() allows us to use a bit more than what was asked at kmalloc()
time, because of discrete kmem caches sizes.

We probably need to instruct kmemcheck of this.
Comment 3 Anonymous Emailer 2011-01-21 08:28:21 UTC
Reply-To: penberg@kernel.org

On 1/20/11 10:41 PM, Eric Dumazet wrote:
> Le jeudi 20 janvier 2011 à 12:25 -0800, Andrew Morton a écrit :
>> (switched to email.  Please respond via emailed reply-to-all, not via the
>> bugzilla web interface).
>>
>> On Thu, 20 Jan 2011 20:08:32 GMT
>> bugzilla-daemon@bugzilla.kernel.org wrote:
>>
>>> https://bugzilla.kernel.org/show_bug.cgi?id=27212
>>>
>>>             Summary: Warning kmemcheck: Caught 64-bit read from
>>>                      uninitialized memory in netlink_broadcast_filtered
>>>             Product: Other
>>>             Version: 2.5
>>>      Kernel Version: 2.6.38-rc1
>>>            Platform: All
>>>          OS/Version: Linux
>>>                Tree: Mainline
>>>              Status: NEW
>>>            Severity: normal
>>>            Priority: P1
>>>           Component: Other
>>>          AssignedTo: other_other@kernel-bugs.osdl.org
>>>          ReportedBy: casteyde.christian@free.fr
>>>          Regression: Yes
>>>
>>>
>>> Athlon 64 X2 3000 in 64bits
>>> Slackware64 13.1
>>> Kernel compiled with kmemcheck and other debug options
>>>
>>> At boot I got the following warning:
>>>
>>> PCI: Using ACPI for IRQ routing
>>> PCI: pci_cache_line_size set to 64 bytes
>>> pci 0000:00:00.0: address space collision: [mem 0xe0000000-0xefffffff pref]
>>> conflicts with GART [mem 0x
>>> e0000000-0xefffffff]
>>> reserve RAM buffer: 000000000009fc00 - 000000000009ffff
>>> reserve RAM buffer: 000000003ffb0000 - 000000003fffffff
>>> WARNING: kmemcheck: Caught 64-bit read from uninitialized memory
>>> (ffff88003e170eb0)
>>> 0000000000000000010000000000000000000000000000000000000000000000
>>>   i i i i i i i i i i i i u u u u u u u u u u u u u u u u u u u u
>>>                                   ^
>>>
>>> Pid: 1, comm: swapper Not tainted 2.6.38-rc1 #2 K8 Combo-Z/K8 Combo-Z
>>> RIP: 0010:[<ffffffff8127ad72>]  [<ffffffff8127ad72>] memmove+0x122/0x1a0
>>> RSP: 0018:ffff88003e0b3c60  EFLAGS: 00010202
>>> RAX: ffff88003e170080 RBX: ffff88003e27b500 RCX: 0000000000000020
>>> RDX: 0000000000000018 RSI: ffff88003e170ea0 RDI: ffff88003e1700a0
>>> RBP: ffff88003e0b3c60 R08: 0000000000000001 R09: 0000000000000001
>>> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
>>> R13: 0000000000000080 R14: 0000000000000000 R15: 0000000000000001
>>> FS:  0000000000000000(0000) GS:ffff88003fc00000(0000)
>>> knlGS:0000000000000000
>>> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
>>> CR2: ffff88003e018abc CR3: 0000000001a1c000 CR4: 00000000000006f0
>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>> DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7: 0000000000000400
>>>   [<ffffffff814741c2>] pskb_expand_head+0xc2/0x2a0
>>>   [<ffffffff81498fa7>] netlink_broadcast_filtered+0xa7/0x4a0
>>>   [<ffffffff814993b8>] netlink_broadcast+0x18/0x20
>>>   [<ffffffff8149b884>] genlmsg_mcast+0x144/0x180
>>>   [<ffffffff8149bc4a>] genl_ctrl_event+0xca/0x450
>>>   [<ffffffff8149c75d>] genl_register_mc_group+0x10d/0x2a0
>>>   [<ffffffff81ad9da4>] genl_init+0x6c/0x84
>>>   [<ffffffff810001de>] do_one_initcall+0x3e/0x170
>>>   [<ffffffff81aae6ea>] kernel_init+0x197/0x21b
>>>   [<ffffffff81003254>] kernel_thread_helper+0x4/0x10
>>>   [<ffffffffffffffff>] 0xffffffffffffffff
>>> pnp: PnP ACPI init
>>> ACPI: bus type pnp registered
>>> pnp 00:00: [bus 00-ff]
>>> pnp 00:00: [io  0x0cf8-0x0cff]
>>>
>>> This is specific to 2.6.38-rc1.
>>>
> Likely a false positive after commit ca44ac38
> (net: don't reallocate skb->head unless the current one hasn't the
> needed extra size or is shared)
>
> ksize() allows us to use a bit more than what was asked at kmalloc()
> time, because of discrete kmem caches sizes.
>
> We probably need to instruct kmemcheck of this.

It actually looks like a bug in SLUB+kmemcheck. The 
kmemcheck_slab_alloc() call in slab_post_alloc_hook() should use ksize() 
instead of s->objsize. SLAB seems to do the right thing already. Anyone 
care to send a patch my way?

             Pekka
Comment 4 Eric Dumazet 2011-01-26 09:19:09 UTC
Le jeudi 20 janvier 2011 à 12:25 -0800, Andrew Morton a écrit :
> (switched to email.  Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
> 
> On Thu, 20 Jan 2011 20:08:32 GMT
> bugzilla-daemon@bugzilla.kernel.org wrote:
> 
> > https://bugzilla.kernel.org/show_bug.cgi?id=27212
> > 
> >            Summary: Warning kmemcheck: Caught 64-bit read from
> >                     uninitialized memory in netlink_broadcast_filtered
> >            Product: Other
> >            Version: 2.5
> >     Kernel Version: 2.6.38-rc1
> >           Platform: All
> >         OS/Version: Linux
> >               Tree: Mainline
> >             Status: NEW
> >           Severity: normal
> >           Priority: P1
> >          Component: Other
> >         AssignedTo: other_other@kernel-bugs.osdl.org
> >         ReportedBy: casteyde.christian@free.fr
> >         Regression: Yes
> > 
> > 
> > Athlon 64 X2 3000 in 64bits
> > Slackware64 13.1
> > Kernel compiled with kmemcheck and other debug options
> > 
> > At boot I got the following warning:
> > 
> > PCI: Using ACPI for IRQ routing
> > PCI: pci_cache_line_size set to 64 bytes
> > pci 0000:00:00.0: address space collision: [mem 0xe0000000-0xefffffff pref]
> > conflicts with GART [mem 0x
> > e0000000-0xefffffff]
> > reserve RAM buffer: 000000000009fc00 - 000000000009ffff 
> > reserve RAM buffer: 000000003ffb0000 - 000000003fffffff
> > WARNING: kmemcheck: Caught 64-bit read from uninitialized memory
> > (ffff88003e170eb0)
> > 0000000000000000010000000000000000000000000000000000000000000000
> >  i i i i i i i i i i i i u u u u u u u u u u u u u u u u u u u u
> >                                  ^
> > 
> > Pid: 1, comm: swapper Not tainted 2.6.38-rc1 #2 K8 Combo-Z/K8 Combo-Z
> > RIP: 0010:[<ffffffff8127ad72>]  [<ffffffff8127ad72>] memmove+0x122/0x1a0
> > RSP: 0018:ffff88003e0b3c60  EFLAGS: 00010202
> > RAX: ffff88003e170080 RBX: ffff88003e27b500 RCX: 0000000000000020
> > RDX: 0000000000000018 RSI: ffff88003e170ea0 RDI: ffff88003e1700a0
> > RBP: ffff88003e0b3c60 R08: 0000000000000001 R09: 0000000000000001
> > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> > R13: 0000000000000080 R14: 0000000000000000 R15: 0000000000000001
> > FS:  0000000000000000(0000) GS:ffff88003fc00000(0000)
> knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> > CR2: ffff88003e018abc CR3: 0000000001a1c000 CR4: 00000000000006f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7: 0000000000000400
> >  [<ffffffff814741c2>] pskb_expand_head+0xc2/0x2a0
> >  [<ffffffff81498fa7>] netlink_broadcast_filtered+0xa7/0x4a0
> >  [<ffffffff814993b8>] netlink_broadcast+0x18/0x20
> >  [<ffffffff8149b884>] genlmsg_mcast+0x144/0x180
> >  [<ffffffff8149bc4a>] genl_ctrl_event+0xca/0x450
> >  [<ffffffff8149c75d>] genl_register_mc_group+0x10d/0x2a0
> >  [<ffffffff81ad9da4>] genl_init+0x6c/0x84
> >  [<ffffffff810001de>] do_one_initcall+0x3e/0x170
> >  [<ffffffff81aae6ea>] kernel_init+0x197/0x21b
> >  [<ffffffff81003254>] kernel_thread_helper+0x4/0x10
> >  [<ffffffffffffffff>] 0xffffffffffffffff
> > pnp: PnP ACPI init
> > ACPI: bus type pnp registered
> > pnp 00:00: [bus 00-ff]
> > pnp 00:00: [io  0x0cf8-0x0cff]
> > 
> > This is specific to 2.6.38-rc1.
> > 

[PATCH] net: add kmemcheck annotation in __alloc_skb()

pskb_expand_head() triggers a kmemcheck warning when copy of
skb_shared_info is done in pskb_expand_head()

This is because destructor_arg field is not necessarily initialized at
this point. Add kmemcheck_annotate_variable() call in __alloc_skb() to
instruct kmemcheck this is a normal situation.

Resolves bugzilla.kernel.org 27212

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=27212
Reported-by: Christian Casteyde <casteyde.christian@free.fr>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Andrew Morton <akpm@linux-foundation.org>
---
 net/core/skbuff.c |    1 +
 1 files changed, 1 insertion(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index d31bb36..1762e97 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -210,6 +210,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 	shinfo = skb_shinfo(skb);
 	memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
 	atomic_set(&shinfo->dataref, 1);
+	kmemcheck_annotate_variable(shinfo->destructor_arg);
 
 	if (fclone) {
 		struct sk_buff *child = skb + 1;
Comment 5 David S. Miller 2011-01-27 22:41:17 UTC
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 26 Jan 2011 10:18:38 +0100

> [PATCH] net: add kmemcheck annotation in __alloc_skb()
> 
> pskb_expand_head() triggers a kmemcheck warning when copy of
> skb_shared_info is done in pskb_expand_head()
> 
> This is because destructor_arg field is not necessarily initialized at
> this point. Add kmemcheck_annotate_variable() call in __alloc_skb() to
> instruct kmemcheck this is a normal situation.
> 
> Resolves bugzilla.kernel.org 27212
> 
> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=27212
> Reported-by: Christian Casteyde <casteyde.christian@free.fr>
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> CC: Andrew Morton <akpm@linux-foundation.org>

Applied, thanks Eric.
Comment 6 Christian Casteyde 2011-02-13 14:00:53 UTC
Update: Still present in -rc4, even if the previous patch was applied.
On another computer (a laptop, the previous one is retired), I get the following warning, that seems to be exactly the same:

eth1: RX AssocResp from c2:2a:2e:a2:2e:38 (capab=0x411 status=0 aid=1)
eth1: associated
ADDRCONF(NETDEV_CHANGE): eth1: link becomes ready
WARNING: kmemcheck: Caught 64-bit read from uninitialized memory (ffff88004b234400)
0000000000000000010000000000000000000000000000000000000000000000
 u u u u u u u u u u u u u u u u u u u u u u u u u u u u u u u u
 ^

Pid: 1883, comm: dhcpcd Not tainted 2.6.38-rc4 #2 Aspire 1510/Aspire 1510  
RIP: 0010:[<ffffffff81257b00>]  [<ffffffff81257b00>] memmove+0x30/0x1a0
RSP: 0018:ffff88004bbf9898  EFLAGS: 00010206
RAX: ffff88004b234400 RBX: ffff88004ba6ce00 RCX: 0000000000000020
RDX: 000000000000016f RSI: ffff88004b234400 RDI: ffff88004b234400
RBP: ffff88004bbf9898 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000200 R14: 0000000000000000 R15: 0000000000000001
FS:  00007fc8ae8f3700(0000) GS:ffffffff81a1b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff88004a82fcb8 CR3: 000000004b281000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7: 0000000000000400
 [<ffffffff8146cff8>] pskb_expand_head+0xd8/0x2a0
 [<ffffffff815b060b>] ieee80211_skb_resize+0x9b/0x120
 [<ffffffff815b29e4>] ieee80211_xmit+0xa4/0x280
 [<ffffffff815b41a6>] ieee80211_subif_start_xmit+0x3e6/0x910
 [<ffffffff81476f44>] dev_hard_start_xmit+0x384/0x6a0
 [<ffffffff8148d354>] sch_direct_xmit+0xd4/0x260
 [<ffffffff81477432>] dev_queue_xmit+0x1d2/0x6f0
 [<ffffffff81554f5e>] packet_sendmsg+0x9de/0xba0
 [<ffffffff814628aa>] sock_sendmsg+0xba/0xf0
 [<ffffffff814631f4>] sys_sendto+0x134/0x180
 [<ffffffff81002478>] system_call_fastpath+0x16/0x1b
 [<ffffffffffffffff>] 0xffffffffffffffff
eth1: no IPv6 routers present

Please note that this is a wireless network on that laptop (broadcom BCM 43xx).
Comment 7 Anonymous Emailer 2011-02-15 05:48:50 UTC
Reply-To: penberg@kernel.org

On Mon, Feb 14, 2011 at 7:35 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> Le vendredi 21 janvier 2011 à 09:49 +0200, Pekka Enberg a écrit :
>
>> It actually looks like a bug in SLUB+kmemcheck. The
>> kmemcheck_slab_alloc() call in slab_post_alloc_hook() should use ksize()
>> instead of s->objsize. SLAB seems to do the right thing already. Anyone
>> care to send a patch my way?
>>
>
> Hmm, what do you think of following patch ?
>
> Thanks, and sorry for the delay.

Looks good to me. Christoph, David, any objections to the patch?

> [PATCH] slub: fix kmemcheck calls to match ksize() hints
>
> Recent use of ksize() in network stack (commit ca44ac38 : net: don't
> reallocate skb->head unless the current one hasn't the needed extra size
> or is shared) triggers kmemcheck warnings, because ksize() can return
> more space than kmemcheck is aware of.
>
> Pekka Enberg noticed SLAB+kmemcheck is doing the right thing, while SLUB
> +kmemcheck doesnt.
>
> Bugzilla reference #27212
>
> Reported-by: Christian Casteyde <casteyde.christian@free.fr>
> Suggested-by: Pekka Enberg <penberg@kernel.org>
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> CC: David Miller <davem@davemloft.net>
> CC: Changli Gao <xiaosuo@gmail.com>
> CC: Andrew Morton <akpm@linux-foundation.org>
> ---
>  mm/slub.c |   49 ++++++++++++++++++++++++++-----------------------
>  1 file changed, 26 insertions(+), 23 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index e15aa7f..ee0aeb8 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -797,10 +797,34 @@ static inline int slab_pre_alloc_hook(struct kmem_cache
> *s, gfp_t flags)
>        return should_failslab(s->objsize, flags, s->flags);
>  }
>
> +static inline size_t slab_ksize(const struct kmem_cache *s)
> +{
> +#ifdef CONFIG_SLUB_DEBUG
> +       /*
> +        * Debugging requires use of the padding between object
> +        * and whatever may come after it.
> +        */
> +       if (s->flags & (SLAB_RED_ZONE | SLAB_POISON))
> +               return s->objsize;
> +
> +#endif
> +       /*
> +        * If we have the need to store the freelist pointer
> +        * back there or track user information then we can
> +        * only use the space before that information.
> +        */
> +       if (s->flags & (SLAB_DESTROY_BY_RCU | SLAB_STORE_USER))
> +               return s->inuse;
> +       /*
> +        * Else we can use all the padding etc for the allocation
> +        */
> +       return s->size;
> +}
> +
>  static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
> void *object)
>  {
>        flags &= gfp_allowed_mask;
> -       kmemcheck_slab_alloc(s, flags, object, s->objsize);
> +       kmemcheck_slab_alloc(s, flags, object, slab_ksize(s));
>        kmemleak_alloc_recursive(object, s->objsize, 1, s->flags, flags);
>  }
>
> @@ -2696,7 +2720,6 @@ EXPORT_SYMBOL(__kmalloc_node);
>  size_t ksize(const void *object)
>  {
>        struct page *page;
> -       struct kmem_cache *s;
>
>        if (unlikely(object == ZERO_SIZE_PTR))
>                return 0;
> @@ -2707,28 +2730,8 @@ size_t ksize(const void *object)
>                WARN_ON(!PageCompound(page));
>                return PAGE_SIZE << compound_order(page);
>        }
> -       s = page->slab;
>
> -#ifdef CONFIG_SLUB_DEBUG
> -       /*
> -        * Debugging requires use of the padding between object
> -        * and whatever may come after it.
> -        */
> -       if (s->flags & (SLAB_RED_ZONE | SLAB_POISON))
> -               return s->objsize;
> -
> -#endif
> -       /*
> -        * If we have the need to store the freelist pointer
> -        * back there or track user information then we can
> -        * only use the space before that information.
> -        */
> -       if (s->flags & (SLAB_DESTROY_BY_RCU | SLAB_STORE_USER))
> -               return s->inuse;
> -       /*
> -        * Else we can use all the padding etc for the allocation
> -        */
> -       return s->size;
> +       return slab_ksize(page->slab);
>  }
>  EXPORT_SYMBOL(ksize);
>
>
>
> --
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Comment 8 Anonymous Emailer 2011-02-15 17:41:07 UTC
Reply-To: cl@linux.com

On Tue, 15 Feb 2011, Pekka Enberg wrote:

> Looks good to me. Christoph, David, any objections to the patch?

My eyes hurt. Is there some way you could use tabs or spaces instead of
these weird symbols?

If the kmemcheck people are fine with checking data beyond the last byte
of the object then its fine with me.

Acked-by: Christoph Lameter <cl@linux.com>
Comment 9 Anonymous Emailer 2011-02-15 17:41:14 UTC
Reply-To: cl@linux.com

On Tue, 15 Feb 2011, Pekka Enberg wrote:

> Looks good to me. Christoph, David, any objections to the patch?

My eyes hurt. Is there some way you could use tabs or spaces instead of
these weird symbols?

If the kmemcheck people are fine with checking data beyond the last byte
of the object then its fine with me.

Acked-by: Christoph Lameter <cl@linux.com>
Comment 10 David Rientjes 2011-02-15 22:21:42 UTC
On Tue, 15 Feb 2011, Pekka Enberg wrote:

> > [PATCH] slub: fix kmemcheck calls to match ksize() hints
> >
> > Recent use of ksize() in network stack (commit ca44ac38 : net: don't
> > reallocate skb->head unless the current one hasn't the needed extra size
> > or is shared) triggers kmemcheck warnings, because ksize() can return
> > more space than kmemcheck is aware of.
> >
> > Pekka Enberg noticed SLAB+kmemcheck is doing the right thing, while SLUB
> > +kmemcheck doesnt.
> >
> > Bugzilla reference #27212
> >
> > Reported-by: Christian Casteyde <casteyde.christian@free.fr>
> > Suggested-by: Pekka Enberg <penberg@kernel.org>
> > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> > CC: David Miller <davem@davemloft.net>
> > CC: Changli Gao <xiaosuo@gmail.com>
> > CC: Andrew Morton <akpm@linux-foundation.org>

Acked-by: David Rientjes <rientjes@google.com>
Comment 11 David Rientjes 2011-02-15 22:56:07 UTC
On Tue, 15 Feb 2011, Pekka Enberg wrote:

> > [PATCH] slub: fix kmemcheck calls to match ksize() hints
> >
> > Recent use of ksize() in network stack (commit ca44ac38 : net: don't
> > reallocate skb->head unless the current one hasn't the needed extra size
> > or is shared) triggers kmemcheck warnings, because ksize() can return
> > more space than kmemcheck is aware of.
> >
> > Pekka Enberg noticed SLAB+kmemcheck is doing the right thing, while SLUB
> > +kmemcheck doesnt.
> >
> > Bugzilla reference #27212
> >
> > Reported-by: Christian Casteyde <casteyde.christian@free.fr>
> > Suggested-by: Pekka Enberg <penberg@kernel.org>
> > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> > CC: David Miller <davem@davemloft.net>
> > CC: Changli Gao <xiaosuo@gmail.com>
> > CC: Andrew Morton <akpm@linux-foundation.org>

Acked-by: David Rientjes <rientjes@google.com>
Comment 12 Florian Mickler 2011-02-19 23:54:40 UTC
merged in .38-rc4:
commit c2aa3665cf8510b1665ee2f5a9525cf7be6dec4f
Author: Eric Dumazet <eric.dumazet@gmail.com>
Date:   Tue Jan 25 23:18:38 2011 +0000

    net: add kmemcheck annotation in __alloc_skb()
Comment 13 Christian Casteyde 2011-02-22 21:30:35 UTC
Update : Still present in 2.6.38-rc6.
Comment 14 Florian Mickler 2011-03-28 23:51:46 UTC
A patch referencing this bug report has been merged in v2.6.38-8876-g036a982:

commit b3d41885d9cd0d9db31c8f49e362bae02c96fa3f
Author: Eric Dumazet <eric.dumazet@gmail.com>
Date:   Mon Feb 14 18:35:22 2011 +0100

    slub: fix kmemcheck calls to match ksize() hints
Comment 15 Christian Casteyde 2011-04-01 20:49:04 UTC
Seems to be fixed in 2.6.38.
Closing.
Comment 16 Florian Mickler 2011-04-01 21:56:08 UTC
Really? That patch went in after 2.6.38 and has not been backported yet...
Comment 17 Christian Casteyde 2011-04-02 15:05:58 UTC
Yes, I didn't managed to reproduce it with 2.6.38.
I won't check it once more, but I'm testing 2.6.39-rc1 and will check that once more.
Comment 18 Christian Casteyde 2011-04-02 17:06:12 UTC
2.6.39-rc1 has a similar, but different, bug (will open another bug):

WARNING: kmemcheck: Caught 64-bit read from uninitialized memory (ffff88004ab13d00)
003eb14a0088ffffb6d50b81ffffffff44616544000000000000000000000000
 u u u u u u u u u u u u u u u u u u u u u u u u u u u u u u u u
 ^

Pid: 1768, comm: ifconfig Not tainted 2.6.39-rc1 #3 Acer,Inc. Aspire 1510  /Aspire 1510
RIP: 0010:[<ffffffff810b9c5d>]  [<ffffffff810b9c5d>] __kmalloc+0xbd/0x1d0
RSP: 0018:ffff88004b8dba78  EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000010 RCX: 00000000000057e1
RDX: 00000000000057e0 RSI: ffff88004fcbf100 RDI: ffffffff8177bcc2
RBP: ffff88004b8dbaa8 R08: ffff880040bb6000 R09: ffff880040444c80
R10: 0000000000000000 R11: ffff880040444ca8 R12: ffff88004ab13d00
R13: ffff88004dc03600 R14: 00000000000080d0 R15: ffffffff814f827d
FS:  00007fbfd42f4700(0000) GS:ffffffff81a1b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: ffff88004ddd39c0 CR3: 000000004b8c9000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7: 0000000000000400
 [<ffffffff814f827d>] tnode_new+0x3d/0x80
 [<ffffffff814f9b4c>] fib_table_insert+0x69c/0x850
 [<ffffffff814f3230>] fib_magic+0xb0/0xc0
 [<ffffffff814f32b1>] fib_add_ifaddr+0x71/0x180
 [<ffffffff814f4490>] fib_inetaddr_event+0x30/0xb0
 [<ffffffff810588e3>] notifier_call_chain+0x83/0x100
 [<ffffffff81058c46>] __blocking_notifier_call_chain+0x76/0xb0
 [<ffffffff81058c91>] blocking_notifier_call_chain+0x11/0x20
 [<ffffffff814e8553>] __inet_insert_ifa+0x1a3/0x240
 [<ffffffff814ea2b5>] devinet_ioctl+0x465/0x8d0
 [<ffffffff814ebd34>] inet_ioctl+0x84/0xa0
 [<ffffffff8146b1cd>] T.1014+0x1d/0x50
 [<ffffffff8146b46d>] sock_ioctl+0x5d/0x2b0
 [<ffffffff810cfe4c>] do_vfs_ioctl+0x9c/0x560
 [<ffffffff810d035a>] sys_ioctl+0x4a/0x80
 [<ffffffff815de4f8>] system_call_fastpath+0x16/0x1b
 [<ffffffffffffffff>] 0xffffffffffffffff

So I've checked 2.6.38.2 to see if it's a regression, and indeed it is. And btw I confirm 2.6.38.2 does not have the problem reported here anymore, maybe it was fixed another way by somebody else.
Comment 19 Florian Mickler 2011-04-02 17:58:04 UTC
Very likely. Thanks for testing. I'm changing the resolution to unreproducible then, as the commit above obviously doesn't fix this.