[PATCH 4.14 17/30] cifs: report error instead of invalid when revalidating a dentry fails

Greg Kroah-Hartman
2021-02-08T15:57:59Z

From: Aurelien Aptel <aaptel@suse.com>

commit 21b200d091826a83aafc95d847139b2b0582f6d1 upstream.

Assuming
- //HOST/a is mounted on /mnt
- //HOST/b is mounted on /mnt/b

On a slow connection, running 'df' and killing it while it's
processing /mnt/b can make cifs_get_inode_info() returns -ERESTARTSYS.

This triggers the following chain of events:
=> the dentry revalidation fail
=> dentry is put and released
=> superblock associated with the dentry is put
=> /mnt/b is unmounted

This patch makes cifs_d_revalidate() return the error instead of 0
(invalid) when cifs_revalidate_dentry() fails, except for ENOENT (file
deleted) and ESTALE (file recreated).

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Suggested-by: Shyam Prasad N <nspmangalore@gmail.com>
Reviewed-by: Shyam Prasad N <nspmangalore@gmail.com>
CC: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/cifs/dir.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)

--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -841,6 +841,7 @@ static int
cifs_d_revalidate(struct dentry *direntry, unsigned int flags)
{
struct inode *inode;
+ int rc;

if (flags & LOOKUP_RCU)
return -ECHILD;
@@ -850,8 +851,25 @@ cifs_d_revalidate(struct dentry *direntr
if ((flags & LOOKUP_REVAL) && !CIFS_CACHE_READ(CIFS_I(inode)))
CIFS_I(inode)->time = 0; /* force reval */

- if (cifs_revalidate_dentry(direntry))
- return 0;
+ rc = cifs_revalidate_dentry(direntry);
+ if (rc) {
+ cifs_dbg(FYI, "cifs_revalidate_dentry failed with rc=%d", rc);
+ switch (rc) {
+ case -ENOENT:
+ case -ESTALE:
+ /*
+ * Those errors mean the dentry is invalid
+ * (file was deleted or recreated)
+ */
+ return 0;
+ default:
+ /*
+ * Otherwise some unexpected error happened
+ * report it as-is to VFS layer
+ */
+ return rc;
+ }
+ }
else {
/*
* If the inode wasn't known to be a dfs entry when