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authorThiago Rafael Becker <trbecker@gmail.com>2021-06-15 13:42:56 -0300
committerSteve French <stfrench@microsoft.com>2021-06-20 21:28:17 -0500
commit6efa994e35a402ae4ae2161b6439c94b64816cee (patch)
tree3ce214fa2764cbc03eacd47bd1d6305cd761eea2 /fs/cifs
parent889c2a700799f3b6f82210925e1faf4a9b833c4a (diff)
cifs: retry lookup and readdir when EAGAIN is returned.
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. Reproducer based on the work by Jacob Shivers: ~~~ $ cat readdir-cifs-test.sh #!/bin/bash # Install and configure powershell and sshd on the windows # server as descibed in # https://docs.microsoft.com/en-us/windows-server/administration/openssh/openssh_overview # This script uses expect(1) USER=dude SERVER=192.168.0.2 RPATH=root PASS='password' function debug_funcs { for line in $@ ; do echo "func $line +p" > /sys/kernel/debug/dynamic_debug/control done } function setup { echo 1 > /proc/fs/cifs/cifsFYI debug_funcs wait_for_compound_request \ smb2_query_dir_first cifs_readdir \ compound_send_recv cifs_reconnect_tcon \ generic_ip_connect cifs_reconnect \ smb2_reconnect_server smb2_reconnect \ cifs_readv_from_socket cifs_readv_receive tcpdump -i eth0 -w cifs.pcap host 192.168.2.182 & sleep 5 dmesg -C } function test_call { if [[ $1 == 1 ]] ; then tracer="strace -tt -f -s 4096 -o trace-$(date -Iseconds).txt" fi # Change the command here to anything appropriate $tracer ls $2 > /dev/null res=$? if [[ $1 == 1 ]] ; then if [[ $res == 0 ]] ; then 1>&2 echo success else 1>&2 echo "failure ($res)" fi fi } mountpoint /mnt > /dev/null || mount -t cifs -o username=$USER,pass=$PASS //$SERVER/$RPATH /mnt test_call 0 /mnt/ /usr/bin/expect << EOF set timeout 60 spawn ssh $USER@$SERVER expect "yes/no" { send "yes\r" expect "*?assword" { send "$PASS\r" } } "*?assword" { send "$PASS\r" } expect ">" { send "powershell close-smbsession -force\r" } expect ">" { send "exit\r" } expect eof EOF sysctl -w vm.drop_caches=2 > /dev/null sysctl -w vm.drop_caches=2 > /dev/null setup test_call 1 /mnt/ ~~~ Signed-off-by: Thiago Rafael Becker <trbecker@gmail.com> Acked-by: Ronnie Sahlberg <lsahlber@redhat.com> Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs/cifs')
-rw-r--r--fs/cifs/dir.c4
-rw-r--r--fs/cifs/smb2ops.c5
2 files changed, 9 insertions, 0 deletions
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/smb2ops.c b/fs/cifs/smb2ops.c
index b68ba92893b6..903de7449aa3 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -2325,6 +2325,7 @@ smb2_query_dir_first(const unsigned int xid, struct cifs_tcon *tcon,
struct smb2_query_directory_rsp *qd_rsp = NULL;
struct smb2_create_rsp *op_rsp = NULL;
struct TCP_Server_Info *server = cifs_pick_channel(tcon->ses);
+ int retry_count = 0;
utf16_path = cifs_convert_path_to_utf16(path, cifs_sb);
if (!utf16_path)
@@ -2372,10 +2373,14 @@ smb2_query_dir_first(const unsigned int xid, struct cifs_tcon *tcon,
smb2_set_related(&rqst[1]);
+again:
rc = compound_send_recv(xid, tcon->ses, server,
flags, 2, rqst,
resp_buftype, rsp_iov);
+ if (rc == -EAGAIN && retry_count++ < 10)
+ goto again;
+
/* If the open failed there is nothing to do */
op_rsp = (struct smb2_create_rsp *)rsp_iov[0].iov_base;
if (op_rsp == NULL || op_rsp->sync_hdr.Status != STATUS_SUCCESS) {