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author | Thiago Rafael Becker <trbecker@gmail.com> | 2021-06-15 13:42:56 -0300 |
---|---|---|
committer | Steve French <stfrench@microsoft.com> | 2021-06-20 21:28:17 -0500 |
commit | 6efa994e35a402ae4ae2161b6439c94b64816cee (patch) | |
tree | 3ce214fa2764cbc03eacd47bd1d6305cd761eea2 /fs/cifs/smb2ops.c | |
parent | 889c2a700799f3b6f82210925e1faf4a9b833c4a (diff) | |
download | linux-6efa994e35a402ae4ae2161b6439c94b64816cee.tar.bz2 |
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/smb2ops.c')
-rw-r--r-- | fs/cifs/smb2ops.c | 5 |
1 files changed, 5 insertions, 0 deletions
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) { |