[RFC PATCH] cifs: retry lookup and readdir when EAGAIN is returned.

* [RFC PATCH] cifs: retry lookup and readdir when EAGAIN is returned.
@ 2021-06-04 17:41 Thiago Rafael Becker
  2021-06-07  9:32 ` Aurélien Aptel
  0 siblings, 1 reply; 4+ messages in thread
From: Thiago Rafael Becker @ 2021-06-04 17:41 UTC (permalink / raw)
  To: linux-cifs; +Cc: sfrench, samba-technical, tbecker, jshivers

According to the investigation performed by Jacob Shivers at Red Hat,
cifs_lookup and cifs_readdir leak EAGAIN when the user session is
deleted on the server. Fix this issue by implementing a retry with
limits, as is implemented in cifs_revalidate_dentry_attr.

Signed-off-by: Thiago Rafael Becker <trbecker@gmail.com>
---
 fs/cifs/dir.c     | 4 ++++
 fs/cifs/readdir.c | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 6bcd3e8f7cda..7c641f9a3dac 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -630,6 +630,7 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry,
 	struct inode *newInode = NULL;
 	const char *full_path;
 	void *page;
+	int retry_count = 0;
 
 	xid = get_xid();
 
@@ -673,6 +674,7 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry,
 	cifs_dbg(FYI, "Full path: %s inode = 0x%p\n",
 		 full_path, d_inode(direntry));
 
+again:
 	if (pTcon->posix_extensions)
 		rc = smb311_posix_get_inode_info(&newInode, full_path, parent_dir_inode->i_sb, xid);
 	else if (pTcon->unix_ext) {
@@ -687,6 +689,8 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry,
 		/* since paths are not looked up by component - the parent
 		   directories are presumed to be good here */
 		renew_parental_timestamps(direntry);
+	} else if (rc == -EAGAIN && retry_count++ < 10) {
+		goto again;
 	} else if (rc == -ENOENT) {
 		cifs_set_time(direntry, jiffies);
 		newInode = NULL;
diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index 63bfc533c9fb..01e6d41e387f 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -844,9 +844,15 @@ static int cifs_filldir(char *find_entry, struct file *file,
 	struct qstr name;
 	int rc = 0;
 	ino_t ino;
+	int retry_count = 0;
 
+again:
 	rc = cifs_fill_dirent(&de, find_entry, file_info->srch_inf.info_level,
 			      file_info->srch_inf.unicode);
+
+	if (rc == -EAGAIN && retry_count++ < 10)
+		goto again;
+
 	if (rc)
 		return rc;
 
-- 
2.31.1


^ permalink raw reply related	[flat|nested] 4+ messages in thread