ksmbd: use vfs_llseek instead of dereferencing NULL

commit 067baa9a37b32b95fdeabccde4b0cb6a2cf95f96 upstream.

By not checking whether llseek is NULL, this might jump to NULL. Also,
it doesn't check FMODE_LSEEK. Fix this by using vfs_llseek(), which
always does the right thing.

Fixes: f44158485826 ("cifsd: add file operations")
Cc: stable@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: Ronnie Sahlberg <lsahlber@redhat.com>
Cc: Hyunchul Lee <hyc.lee@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ksmbd/vfs.c b/fs/ksmbd/vfs.c
index 02bafd52cd060cb3fc6a65573d44c4ddbbb85675..ce852a12dea682e3fe5623996cd0a81f816aafa8 100644 (file)
--- a/fs/ksmbd/vfs.c
+++ b/fs/ksmbd/vfs.c
@@ -1051,7 +1051,7 @@ int ksmbd_vfs_fqar_lseek(struct ksmbd_file *fp, loff_t start, loff_t length,
        *out_count = 0;
        end = start + length;
        while (start < end && *out_count < in_count) {
-               extent_start = f->f_op->llseek(f, start, SEEK_DATA);
+               extent_start = vfs_llseek(f, start, SEEK_DATA);
                if (extent_start < 0) {
                        if (extent_start != -ENXIO)
                                ret = (int)extent_start;
@@ -1061,7 +1061,7 @@ int ksmbd_vfs_fqar_lseek(struct ksmbd_file *fp, loff_t start, loff_t length,
                if (extent_start >= end)
                        break;
 
-               extent_end = f->f_op->llseek(f, extent_start, SEEK_HOLE);
+               extent_end = vfs_llseek(f, extent_start, SEEK_HOLE);
                if (extent_end < 0) {
                        if (extent_end != -ENXIO)
                                ret = (int)extent_end;