Exact Kernel version: 2.5.46-mm1 Distribution: Redhat 7.2 / 7.3 Hardware Environment: P4 PC Software Environment: KDE Problem Description: Enabling shared pagetables causes KDE to wierd out Steps to reproduce: Start KDE
This should be fixed in 2.5.49-mm1
A vma with vm_pgoff large enough to overflow a loff_t type when converted to a byte offset can be passed via the remap_file_pages system call. The hugetlbfs mmap routine uses the byte offset to calculate reservations and file size. A sequence such as: mmap(0x20a00000, 0x600000, 0, 0x66033, -1, 0); remap_file_pages(0x20a00000, 0x600000, 0, 0x20000000000000, 0); will result in the following when task exits/file closed, kernel BUG at mm/hugetlb.c:749! Call Trace: hugetlbfs_evict_inode+0x2f/0x40 evict+0xcb/0x190 __dentry_kill+0xcb/0x150 __fput+0x164/0x1e0 task_work_run+0x84/0xa0 exit_to_usermode_loop+0x7d/0x80 do_syscall_64+0x18b/0x190 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 The overflowed pgoff value causes hugetlbfs to try to set up a mapping with a negative range (end < start) that leaves invalid state which causes the BUG. The previous overflow fix to this code was incomplete and did not take the remap_file_pages system call into account. Fixes: 045c7a3f53d9 ("hugetlbfs: fix offset overflow in hugetlbfs mmap") Cc: <stable@vger.kernel.org> Reported-by: Nic Losby <blurbdust@gmail.com> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> --- Changes in v3 * Use a simpler mask computation as suggested by Andrew Morton Changes in v2 * Use bitmask for overflow check as suggested by Yisheng Xie * Add explicit (from > to) check when setting up reservations * Cc stable fs/hugetlbfs/inode.c | 16 +++++++++++++--- mm/hugetlb.c | 6 ++++++ 2 files changed, 19 insertions(+), 3 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 8fe1b0aa2896..e46117dc006a 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -108,6 +108,15 @@ static void huge_pagevec_release(struct pagevec *pvec) pagevec_reinit(pvec); } +/* + * Mask used when checking the page offset value passed in via system + * calls. This value will be converted to a loff_t which is signed. + * Therefore, we want to check the upper PAGE_SHIFT + 1 bits of the + * value. The extra bit (- 1 in the shift value) is to take the sign + * bit into account. + */ +#define PGOFF_LOFFT_MAX (PAGE_MASK << (BITS_PER_LONG - (2 * PAGE_SHIFT) - 1)) + static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) { struct inode *inode = file_inode(file); @@ -127,12 +136,13 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) vma->vm_ops = &hugetlb_vm_ops; /* - * Offset passed to mmap (before page shift) could have been - * negative when represented as a (l)off_t. + * page based offset in vm_pgoff could be sufficiently large to + * overflow a (l)off_t when converted to byte offset. */ - if (((loff_t)vma->vm_pgoff << PAGE_SHIFT) < 0) + if (vma->vm_pgoff & PGOFF_LOFFT_MAX) return -EINVAL; + /* must be huge page aligned */ if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT)) return -EINVAL; diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 7c204e3d132b..8eeade0a0b7a 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4374,6 +4374,12 @@ int hugetlb_reserve_pages(struct inode *inode, struct resv_map *resv_map; long gbl_reserve; + /* This should never happen */ + if (from > to) { + VM_WARN(1, "%s called with a negative range\n", __func__); + return -EINVAL; + } + /* * Only apply hugepage reservation if asked. At fault time, an * attempt will be made for VM_NORESERVE to allocate a page
On Thu, 8 Mar 2018 16:27:26 -0800 Mike Kravetz <mike.kravetz@oracle.com> wrote: > A vma with vm_pgoff large enough to overflow a loff_t type when > converted to a byte offset can be passed via the remap_file_pages > system call. The hugetlbfs mmap routine uses the byte offset to > calculate reservations and file size. > > A sequence such as: > mmap(0x20a00000, 0x600000, 0, 0x66033, -1, 0); > remap_file_pages(0x20a00000, 0x600000, 0, 0x20000000000000, 0); > will result in the following when task exits/file closed, > kernel BUG at mm/hugetlb.c:749! > Call Trace: > hugetlbfs_evict_inode+0x2f/0x40 > evict+0xcb/0x190 > __dentry_kill+0xcb/0x150 > __fput+0x164/0x1e0 > task_work_run+0x84/0xa0 > exit_to_usermode_loop+0x7d/0x80 > do_syscall_64+0x18b/0x190 > entry_SYSCALL_64_after_hwframe+0x3d/0xa2 > > The overflowed pgoff value causes hugetlbfs to try to set up a > mapping with a negative range (end < start) that leaves invalid > state which causes the BUG. > > The previous overflow fix to this code was incomplete and did not > take the remap_file_pages system call into account. > > ... > > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -4374,6 +4374,12 @@ int hugetlb_reserve_pages(struct inode *inode, > struct resv_map *resv_map; > long gbl_reserve; > > + /* This should never happen */ > + if (from > to) { > + VM_WARN(1, "%s called with a negative range\n", __func__); > + return -EINVAL; > + } This is tidier, and that comment is a bit too obvious to live ;) --- a/mm/hugetlb.c~hugetlbfs-check-for-pgoff-value-overflow-v3-fix +++ a/mm/hugetlb.c @@ -18,6 +18,7 @@ #include <linux/bootmem.h> #include <linux/sysfs.h> #include <linux/slab.h> +#include <linux/mmdebug.h> #include <linux/sched/signal.h> #include <linux/rmap.h> #include <linux/string_helpers.h> @@ -4374,11 +4375,8 @@ int hugetlb_reserve_pages(struct inode * struct resv_map *resv_map; long gbl_reserve; - /* This should never happen */ - if (from > to) { - VM_WARN(1, "%s called with a negative range\n", __func__); + if (VM_WARN(from > to, "%s called with a negative range\n", __func__)) return -EINVAL; - } /* * Only apply hugepage reservation if asked. At fault time, an
On Thu 08-03-18 16:27:26, Mike Kravetz wrote: > A vma with vm_pgoff large enough to overflow a loff_t type when > converted to a byte offset can be passed via the remap_file_pages > system call. The hugetlbfs mmap routine uses the byte offset to > calculate reservations and file size. > > A sequence such as: > mmap(0x20a00000, 0x600000, 0, 0x66033, -1, 0); > remap_file_pages(0x20a00000, 0x600000, 0, 0x20000000000000, 0); > will result in the following when task exits/file closed, > kernel BUG at mm/hugetlb.c:749! > Call Trace: > hugetlbfs_evict_inode+0x2f/0x40 > evict+0xcb/0x190 > __dentry_kill+0xcb/0x150 > __fput+0x164/0x1e0 > task_work_run+0x84/0xa0 > exit_to_usermode_loop+0x7d/0x80 > do_syscall_64+0x18b/0x190 > entry_SYSCALL_64_after_hwframe+0x3d/0xa2 > > The overflowed pgoff value causes hugetlbfs to try to set up a > mapping with a negative range (end < start) that leaves invalid > state which causes the BUG. > > The previous overflow fix to this code was incomplete and did not > take the remap_file_pages system call into account. > > Fixes: 045c7a3f53d9 ("hugetlbfs: fix offset overflow in hugetlbfs mmap") > Cc: <stable@vger.kernel.org> > Reported-by: Nic Losby <blurbdust@gmail.com> > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> OK, looks good to me. Hairy but seems to be the easiest way around this. Acked-by: Michal Hocko <mhocko@suse.com> > --- > Changes in v3 > * Use a simpler mask computation as suggested by Andrew Morton > Changes in v2 > * Use bitmask for overflow check as suggested by Yisheng Xie > * Add explicit (from > to) check when setting up reservations > * Cc stable > > fs/hugetlbfs/inode.c | 16 +++++++++++++--- > mm/hugetlb.c | 6 ++++++ > 2 files changed, 19 insertions(+), 3 deletions(-) > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index 8fe1b0aa2896..e46117dc006a 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -108,6 +108,15 @@ static void huge_pagevec_release(struct pagevec *pvec) > pagevec_reinit(pvec); > } > > +/* > + * Mask used when checking the page offset value passed in via system > + * calls. This value will be converted to a loff_t which is signed. > + * Therefore, we want to check the upper PAGE_SHIFT + 1 bits of the > + * value. The extra bit (- 1 in the shift value) is to take the sign > + * bit into account. > + */ > +#define PGOFF_LOFFT_MAX (PAGE_MASK << (BITS_PER_LONG - (2 * PAGE_SHIFT) - > 1)) > + > static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct > *vma) > { > struct inode *inode = file_inode(file); > @@ -127,12 +136,13 @@ static int hugetlbfs_file_mmap(struct file *file, > struct vm_area_struct *vma) > vma->vm_ops = &hugetlb_vm_ops; > > /* > - * Offset passed to mmap (before page shift) could have been > - * negative when represented as a (l)off_t. > + * page based offset in vm_pgoff could be sufficiently large to > + * overflow a (l)off_t when converted to byte offset. > */ > - if (((loff_t)vma->vm_pgoff << PAGE_SHIFT) < 0) > + if (vma->vm_pgoff & PGOFF_LOFFT_MAX) > return -EINVAL; > > + /* must be huge page aligned */ > if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT)) > return -EINVAL; > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 7c204e3d132b..8eeade0a0b7a 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -4374,6 +4374,12 @@ int hugetlb_reserve_pages(struct inode *inode, > struct resv_map *resv_map; > long gbl_reserve; > > + /* This should never happen */ > + if (from > to) { > + VM_WARN(1, "%s called with a negative range\n", __func__); > + return -EINVAL; > + } > + > /* > * Only apply hugepage reservation if asked. At fault time, an > * attempt will be made for VM_NORESERVE to allocate a page > -- > 2.13.6
On 03/16/2018 03:17 AM, Michal Hocko wrote: > On Thu 08-03-18 16:27:26, Mike Kravetz wrote: > > OK, looks good to me. Hairy but seems to be the easiest way around this. > Acked-by: Michal Hocko <mhocko@suse.com> > <snip> >> +/* >> + * Mask used when checking the page offset value passed in via system >> + * calls. This value will be converted to a loff_t which is signed. >> + * Therefore, we want to check the upper PAGE_SHIFT + 1 bits of the >> + * value. The extra bit (- 1 in the shift value) is to take the sign >> + * bit into account. >> + */ >> +#define PGOFF_LOFFT_MAX (PAGE_MASK << (BITS_PER_LONG - (2 * PAGE_SHIFT) - >> 1)) Thanks Michal, However, kbuild found a problem with this definition on certain configs. Consider a config where, BITS_PER_LONG = 32 (32bit config) PAGE_SHIFT = 16 (64K pages) This results in the negative shift value. Not something I would not immediately think of, but a valid config. The definition has been changed to, #define PGOFF_LOFFT_MAX \ (((1UL << (PAGE_SHIFT + 1)) - 1) << (BITS_PER_LONG - (PAGE_SHIFT + 1))) as discussed here, http://lkml.kernel.org/r/432fb2a3-b729-9c3a-7d60-890b8f9b10dd@oracle.com
On Fri 16-03-18 09:19:07, Mike Kravetz wrote: > On 03/16/2018 03:17 AM, Michal Hocko wrote: > > On Thu 08-03-18 16:27:26, Mike Kravetz wrote: > > > > OK, looks good to me. Hairy but seems to be the easiest way around this. > > Acked-by: Michal Hocko <mhocko@suse.com> > > > <snip> > >> +/* > >> + * Mask used when checking the page offset value passed in via system > >> + * calls. This value will be converted to a loff_t which is signed. > >> + * Therefore, we want to check the upper PAGE_SHIFT + 1 bits of the > >> + * value. The extra bit (- 1 in the shift value) is to take the sign > >> + * bit into account. > >> + */ > >> +#define PGOFF_LOFFT_MAX (PAGE_MASK << (BITS_PER_LONG - (2 * PAGE_SHIFT) - > 1)) > > Thanks Michal, > > However, kbuild found a problem with this definition on certain configs. > Consider a config where, > BITS_PER_LONG = 32 (32bit config) > PAGE_SHIFT = 16 (64K pages) > This results in the negative shift value. > Not something I would not immediately think of, but a valid config. Well, 64K pages on 32b doesn't sound even remotely sane to me but what ever. > The definition has been changed to, > #define PGOFF_LOFFT_MAX \ > (((1UL << (PAGE_SHIFT + 1)) - 1) << (BITS_PER_LONG - (PAGE_SHIFT + > 1))) > > as discussed here, > http://lkml.kernel.org/r/432fb2a3-b729-9c3a-7d60-890b8f9b10dd@oracle.com This looks more wild but seems correct as well. You can keep my acked-by Thanks!