nilfs2: reject zero bd_oblocknr in nilfs_ioctl_mark_blocks_dirty()

nilfs_ioctl_mark_blocks_dirty() uses bd_oblocknr to detect dead blocks
by comparing it with the current block number bd_blocknr. If they differ,
the block is considered dead and skipped.

However, bd_oblocknr should never be 0 since block 0 typically stores the
primary superblock and is never a valid GC target block. A corrupted ioctl
request with bd_oblocknr set to 0 causes the comparison to incorrectly
match when the lookup returns -ENOENT and sets bd_blocknr to 0, bypassing
the dead block check and calling nilfs_bmap_mark() on a non-existent
block. This causes nilfs_btree_do_lookup() to return -ENOENT, triggering
the WARN_ON(ret == -ENOENT).

Fix this by rejecting ioctl requests with bd_oblocknr set to 0 at the
beginning of each iteration.

[ryusuke: slightly modified the commit message and comments for accuracy]

Fixes: 7942b919f732 ("nilfs2: ioctl operations")
Reported-by: syzbot+98a040252119df0506f8@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=98a040252119df0506f8
Suggested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
Reported-by: syzbot+466a45fcfb0562f5b9a0@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=466a45fcfb0562f5b9a0
Cc: Junjie Cao <junjie.cao@linux.dev>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index e17b8da66491334e2d3d182e84ac6ec08275eb85..e0a606643e879292fb524070bf91d2a86be4b906 100644 (file)
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -736,6 +736,12 @@ static int nilfs_ioctl_mark_blocks_dirty(struct the_nilfs *nilfs,
        int ret, i;
 
        for (i = 0; i < nmembs; i++) {
+               /*
+                * bd_oblocknr must never be 0 as block 0
+                * is never a valid GC target block
+                */
+               if (unlikely(!bdescs[i].bd_oblocknr))
+                       return -EINVAL;
                /* XXX: use macro or inline func to check liveness */
                ret = nilfs_bmap_lookup_at_level(bmap,
                                                 bdescs[i].bd_offset,