[PATCH 5.15 05/98] ksmbd: use vfs_llseek instead of dereferencing NULL

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Jason A. Donenfeld <Jason@zx2c4.com>

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>
---
 fs/ksmbd/vfs.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/ksmbd/vfs.c
+++ b/fs/ksmbd/vfs.c
@@ -1051,7 +1051,7 @@ int ksmbd_vfs_fqar_lseek(struct ksmbd_fi
 	*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_fi
 		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;