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authorJiachen Zhang <zhangjiachen.jaycee@bytedance.com>2022-07-28 19:49:15 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-08-25 11:14:54 +0200
commit04e0ac5434ce8c0ec3f6ba7564896bf20e976be2 (patch)
treeec100a84e55aa3be8516562375b2f1b05f8da61e /fs/overlayfs
parent7f77dcbc030c2faa6d8e8a594985eeb34018409e (diff)
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ovl: drop WARN_ON() dentry is NULL in ovl_encode_fh()
commit dd524b7f317de8d31d638cbfdc7be4cf9b770e42 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/overlayfs')
-rw-r--r--fs/overlayfs/export.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index ba6c7c59261a..271f8c9fe253 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -277,7 +277,7 @@ 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;
type = ovl_dentry_to_fh(dentry, fid, max_len);