[PATCH] f2fs: fix to avoid uninit-value access in f2fs_sanity_check_node_footer

[PATCH] f2fs: fix to avoid uninit-value access in f2fs_sanity_check_node_footer

[Chao Yu]

syzbot reported a f2fs bug as below:

BUG: KMSAN: uninit-value in f2fs_sanity_check_node_footer+0x374/0xa20 fs/f2fs/node.c:1520
 f2fs_sanity_check_node_footer+0x374/0xa20 fs/f2fs/node.c:1520
 f2fs_finish_read_bio+0xe1e/0x1d60 fs/f2fs/data.c:177
 f2fs_read_end_io+0x6ab/0x2220 fs/f2fs/data.c:-1
 bio_endio+0x1006/0x1160 block/bio.c:1792
 submit_bio_noacct+0x533/0x2960 block/blk-core.c:891
 submit_bio+0x57a/0x620 block/blk-core.c:926
 blk_crypto_submit_bio include/linux/blk-crypto.h:203 [inline]
 f2fs_submit_read_bio+0x12c/0x360 fs/f2fs/data.c:557
 f2fs_submit_page_bio+0xee2/0x1450 fs/f2fs/data.c:775
 read_node_folio+0x384/0x4b0 fs/f2fs/node.c:1481
 __get_node_folio+0x5db/0x15d0 fs/f2fs/node.c:1576
 f2fs_get_inode_folio+0x40/0x50 fs/f2fs/node.c:1623
 do_read_inode fs/f2fs/inode.c:425 [inline]
 f2fs_iget+0x1209/0x9380 fs/f2fs/inode.c:596
 f2fs_fill_super+0x8f5a/0xb2e0 fs/f2fs/super.c:5184
 get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
 get_tree_bdev+0x38/0x50 fs/super.c:1717
 f2fs_get_tree+0x35/0x40 fs/f2fs/super.c:5436
 vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3763 [inline]
 do_new_mount+0x885/0x1dd0 fs/namespace.c:3839
 path_mount+0x7a2/0x20b0 fs/namespace.c:4159
 do_mount fs/namespace.c:4172 [inline]
 __do_sys_mount fs/namespace.c:4361 [inline]
 __se_sys_mount+0x704/0x7f0 fs/namespace.c:4338
 __x64_sys_mount+0xe4/0x150 fs/namespace.c:4338
 x64_sys_call+0x39f0/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The root cause is: in f2fs_finish_read_bio(), we may access uninit data
in folio if we failed to read the data from device into folio, let's add
a check condition to avoid such issue.

Cc: stable@kernel.org
Fixes: 50ac3ecd8e05 ("f2fs: fix to do sanity check on node footer in {read,write}_end_io")
Reported-by: syzbot+9aac813cdc456cdd49f8@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-f2fs-devel/69a9ca26.a70a0220.305d9a.0000.GAE@google.com
Signed-off-by: Chao Yu <chao@kernel.org>
---
 fs/f2fs/data.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 400f0400e13d..cb2332faf5f0 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -173,7 +173,8 @@ static void f2fs_finish_read_bio(struct bio *bio, bool in_task)
 		while (nr_pages--)
 			dec_page_count(F2FS_F_SB(folio), __read_io_type(folio));
 
-		if (F2FS_F_SB(folio)->node_inode && is_node_folio(folio) &&
+		if (bio->bi_status == BLK_STS_OK &&
+			F2FS_F_SB(folio)->node_inode && is_node_folio(folio) &&
 			f2fs_sanity_check_node_footer(F2FS_F_SB(folio),
 				folio, folio->index, NODE_TYPE_REGULAR, true))
 			bio->bi_status = BLK_STS_IOERR;
-- 
2.49.0

Re: [f2fs-dev] [PATCH] f2fs: fix to avoid uninit-value access in f2fs_sanity_check_node_footer

[patchwork-bot+f2fs]

Hello:

This patch was applied to jaegeuk/f2fs.git (dev)
by Jaegeuk Kim <jaegeuk@kernel.org>:

On Mon,  9 Mar 2026 02:22:37 +0000 you wrote:
> syzbot reported a f2fs bug as below:
> 
> BUG: KMSAN: uninit-value in f2fs_sanity_check_node_footer+0x374/0xa20 fs/f2fs/node.c:1520
>  f2fs_sanity_check_node_footer+0x374/0xa20 fs/f2fs/node.c:1520
>  f2fs_finish_read_bio+0xe1e/0x1d60 fs/f2fs/data.c:177
>  f2fs_read_end_io+0x6ab/0x2220 fs/f2fs/data.c:-1
>  bio_endio+0x1006/0x1160 block/bio.c:1792
>  submit_bio_noacct+0x533/0x2960 block/blk-core.c:891
>  submit_bio+0x57a/0x620 block/blk-core.c:926
>  blk_crypto_submit_bio include/linux/blk-crypto.h:203 [inline]
>  f2fs_submit_read_bio+0x12c/0x360 fs/f2fs/data.c:557
>  f2fs_submit_page_bio+0xee2/0x1450 fs/f2fs/data.c:775
>  read_node_folio+0x384/0x4b0 fs/f2fs/node.c:1481
>  __get_node_folio+0x5db/0x15d0 fs/f2fs/node.c:1576
>  f2fs_get_inode_folio+0x40/0x50 fs/f2fs/node.c:1623
>  do_read_inode fs/f2fs/inode.c:425 [inline]
>  f2fs_iget+0x1209/0x9380 fs/f2fs/inode.c:596
>  f2fs_fill_super+0x8f5a/0xb2e0 fs/f2fs/super.c:5184
>  get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
>  get_tree_bdev+0x38/0x50 fs/super.c:1717
>  f2fs_get_tree+0x35/0x40 fs/f2fs/super.c:5436
>  vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
>  fc_mount fs/namespace.c:1193 [inline]
>  do_new_mount_fc fs/namespace.c:3763 [inline]
>  do_new_mount+0x885/0x1dd0 fs/namespace.c:3839
>  path_mount+0x7a2/0x20b0 fs/namespace.c:4159
>  do_mount fs/namespace.c:4172 [inline]
>  __do_sys_mount fs/namespace.c:4361 [inline]
>  __se_sys_mount+0x704/0x7f0 fs/namespace.c:4338
>  __x64_sys_mount+0xe4/0x150 fs/namespace.c:4338
>  x64_sys_call+0x39f0/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:166
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> [...]

Here is the summary with links:
  - [f2fs-dev] f2fs: fix to avoid uninit-value access in f2fs_sanity_check_node_footer
    https://git.kernel.org/jaegeuk/f2fs/c/7e00e868a0db

You are awesome, thank you!
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