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    Subject[PATCH AUTOSEL 5.13 40/59] cifs: retry lookup and readdir when EAGAIN is returned.
    Date
    From: Thiago Rafael Becker <trbecker@gmail.com>

    [ Upstream commit 6efa994e35a402ae4ae2161b6439c94b64816cee ]

    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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/cifs/dir.c | 4 ++++
    fs/cifs/smb2ops.c | 5 +++++
    2 files changed, 9 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/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) {
    --
    2.30.2
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