The following message appeared during boot: Mar 15 12:09:22 ivy kernel: ================================================================================ Mar 15 12:09:22 ivy kernel: UBSAN: Undefined behaviour in fs/ext4/mballoc.c:2612:15 Mar 15 12:09:22 ivy kernel: shift exponent -1 is negative Mar 15 12:09:22 ivy kernel: CPU: 1 PID: 657 Comm: mount Not tainted 4.5.0-pege1 #1 Mar 15 12:09:22 ivy kernel: Hardware name: Hewlett-Packard HP ENVY dv6 Notebook PC/181B, BIOS F.29 10/03/2013 Mar 15 12:09:22 ivy kernel: 0000000000000000 00000000450d838f ffffffff816fcef7 0000000000000001 Mar 15 12:09:22 ivy kernel: 00000000450d838f ffff880449cfbb90 ffff880449cfbc10 ffffffff817952a9 Mar 15 12:09:22 ivy kernel: ffffffffc324f17e ffffffff81795caa 0000000000000202 000000000000312d Mar 15 12:09:22 ivy kernel: Call Trace: Mar 15 12:09:22 ivy kernel: [<ffffffff816fcef7>] ? dump_stack+0x70/0xb9 Mar 15 12:09:22 ivy kernel: [<ffffffff817952a9>] ? ubsan_epilogue+0x9/0x40 Mar 15 12:09:22 ivy kernel: [<ffffffff81795caa>] ? __ubsan_handle_shift_out_of_bounds+0xfa/0x150 Mar 15 12:09:22 ivy kernel: [<ffffffff81380031>] ? use_mm+0x3e1/0x5d0 Mar 15 12:09:22 ivy kernel: [<ffffffffc310e408>] ? ext4_mb_init+0xbf8/0xf70 [ext4] Mar 15 12:09:22 ivy kernel: [<ffffffffc31146db>] ? ext4_setup_system_zone+0x20b/0x4d0 [ext4] Mar 15 12:09:22 ivy kernel: [<ffffffffc30cbd5e>] ? ext4_fill_super+0x52fe/0x83a0 [ext4] Mar 15 12:09:22 ivy kernel: [<ffffffff817252b9>] ? snprintf+0x49/0x60 Mar 15 12:09:22 ivy kernel: [<ffffffffc30c6a60>] ? ext4_calculate_overhead+0xc90/0xc90 [ext4] Mar 15 12:09:22 ivy kernel: [<ffffffff8145a549>] ? mount_bdev+0x1a9/0x290 Mar 15 12:09:22 ivy kernel: [<ffffffff8145bbba>] ? mount_fs+0x4a/0x280 Mar 15 12:09:22 ivy kernel: [<ffffffff81499906>] ? vfs_kern_mount+0x76/0x290 Mar 15 12:09:22 ivy kernel: [<ffffffff814a118c>] ? do_mount+0x2ac/0x1be0 Mar 15 12:09:22 ivy kernel: [<ffffffff814a0bd5>] ? copy_mount_options+0x35/0x320 Mar 15 12:09:22 ivy kernel: [<ffffffff814a3274>] ? SyS_mount+0x84/0xc0 Mar 15 12:09:22 ivy kernel: [<ffffffff81dfbcf6>] ? entry_SYSCALL_64_fastpath+0x16/0x75 Mar 15 12:09:22 ivy kernel: ================================================================================ Let me know if you need more information.
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 50e05df..8ccfcf7 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -1278,6 +1278,8 @@ static int mb_find_order_for_block(struct ext4_buddy *e4b, int block) /* this block is part of buddy of order 'order' */ return order; } + if (order > e4b->bd_blkbits) + break; bb += 1 << (e4b->bd_blkbits - order); order++; } @@ -2616,6 +2618,8 @@ int ext4_mb_init(struct super_block *sb) do { sbi->s_mb_offsets[i] = offset; sbi->s_mb_maxs[i] = max; + if (i > sb->s_blocksize_bits) + break; offset += 1 << (sb->s_blocksize_bits - i); max = max >> 1; i++; The only case if when i>b you compute off and max but those are not assigned . So those values can be ignored. It keeps the old behaviour intact and fixes the undefined behaviour. offset += 1 << (sb->s_blocksize_bits - i); /* Remove the if to see trap error at runtime */ /* gcc -fsanitize=undefined x.c */ int main() { int i=1; int b=12; unsigned ub=12; unsigned off=0,uoff=0; do{ if(i> b) break; off+=1<<(b-i); uoff+=1<<(ub-i); i++; } while(i<=b+1); }
I will be applying these patches: http://patchwork.ozlabs.org/patch/599805/ http://patchwork.ozlabs.org/patch/599804/