On Thu, Dec 22, 2016 at 01:30:15PM +0100, Alexander Potapenko wrote: > KMSAN (KernelMemorySanitizer, a new error detection tool) reports use of > uninitialized memory in ext4_update_bh_state(): > > ================================================================== > BUG: KMSAN: use of unitialized memory > CPU: 3 PID: 1 Comm: swapper/0 Tainted: G B 4.8.0-rc6+ #597 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs > 01/01/2011 > 0000000000000282 ffff88003cc96f68 ffffffff81f30856 0000003000000008 > ffff88003cc96f78 0000000000000096 ffffffff8169742a ffff88003cc96ff8 > ffffffff812fc1fc 0000000000000008 ffff88003a1980e8 0000000100000000 > Call Trace: > [< inline >] __dump_stack lib/dump_stack.c:15 > [<ffffffff81f30856>] dump_stack+0xa6/0xc0 lib/dump_stack.c:51 > [<ffffffff812fc1fc>] kmsan_report+0x1ec/0x300 mm/kmsan/kmsan.c:? > [<ffffffff812fc33b>] __msan_warning+0x2b/0x40 ??:? > [< inline >] ext4_update_bh_state fs/ext4/inode.c:727 > [<ffffffff8169742a>] _ext4_get_block+0x6ca/0x8a0 fs/ext4/inode.c:759 > [<ffffffff81696d4c>] ext4_get_block+0x8c/0xa0 fs/ext4/inode.c:769 > [<ffffffff814a2d36>] generic_block_bmap+0x246/0x2b0 fs/buffer.c:2991 > [<ffffffff816ca30e>] ext4_bmap+0x5ee/0x660 fs/ext4/inode.c:3177 > ... > origin description: ----tmp@generic_block_bmap > ================================================================== > > (the line numbers are relative to 4.8-rc6, but the bug persists > upstream) > > The local |tmp| is created in generic_block_bmap() and then passed into > ext4_bmap() => ext4_get_block() => _ext4_get_block() => > ext4_update_bh_state(). Along the way tmp.b_page is never initialized > before ext4_update_bh_state() checks its value. > > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> This is a one-line fix to fs/buffer.c; but I've investigated, and since it only affects ext4, and no one else has responded, I'll take the change through the ext4 git tree. Thanks!! - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
