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> --- fs/buffer.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/buffer.c b/fs/buffer.c index d21771f..3fb104e 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -3029,6 +3029,7 @@ sector_t generic_block_bmap(struct address_space *mapping, sector_t block, tmp.b_state = 0; tmp.b_blocknr = 0; tmp.b_size = 1 << inode->i_blkbits; + tmp.b_page = NULL; get_block(inode, block, &tmp, 0); return tmp.b_blocknr; } -- 2.8.0.rc3.226.g39d4020 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
