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| author | Jiachen Zhang <zhangjiachen.jaycee@bytedance.com> | 2022-07-28 19:49:15 +0800 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2022-07-28 15:00:57 +0200 |
| commit | dd524b7f317de8d31d638cbfdc7be4cf9b770e42 (patch) | |
| tree | ecc5b44112661317683b0122eacbe92a91c9f7b4 /fs/overlayfs | |
| parent | ded536561a3674327dfa4bb389085705cae22b8a (diff) | |
| download | lwn-dd524b7f317de8d31d638cbfdc7be4cf9b770e42.tar.gz lwn-dd524b7f317de8d31d638cbfdc7be4cf9b770e42.zip | |
ovl: drop WARN_ON() dentry is NULL in ovl_encode_fh()
Some code paths cannot guarantee the inode have any dentry alias. So
WARN_ON() all !dentry may flood the kernel logs.
For example, when an overlayfs inode is watched by inotifywait (1), and
someone is trying to read the /proc/$(pidof inotifywait)/fdinfo/INOTIFY_FD,
at that time if the dentry has been reclaimed by kernel (such as
echo 2 > /proc/sys/vm/drop_caches), there will be a WARN_ON(). The
printed call stack would be like:
? show_mark_fhandle+0xf0/0xf0
show_mark_fhandle+0x4a/0xf0
? show_mark_fhandle+0xf0/0xf0
? seq_vprintf+0x30/0x50
? seq_printf+0x53/0x70
? show_mark_fhandle+0xf0/0xf0
inotify_fdinfo+0x70/0x90
show_fdinfo.isra.4+0x53/0x70
seq_show+0x130/0x170
seq_read+0x153/0x440
vfs_read+0x94/0x150
ksys_read+0x5f/0xe0
do_syscall_64+0x59/0x1e0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
So let's drop WARN_ON() to avoid kernel log flooding.
Reported-by: Hongbo Yin <yinhongbo@bytedance.com>
Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@bytedance.com>
Signed-off-by: Tianci Zhang <zhangtianci.1997@bytedance.com>
Fixes: 8ed5eec9d6c4 ("ovl: encode pure upper file handles")
Cc: <stable@vger.kernel.org> # v4.16
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/overlayfs')
| -rw-r--r-- | fs/overlayfs/export.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c index 2eada97bbd23..e065a5b9a442 100644 --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -259,7 +259,7 @@ static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len, return FILEID_INVALID; dentry = d_find_any_alias(inode); - if (WARN_ON(!dentry)) + if (!dentry) return FILEID_INVALID; bytes = ovl_dentry_to_fid(ofs, dentry, fid, buflen); |