linux-kernel - [PATCH 5.18 006/102] ksmbd: use vfs_llseek instead of dereferencing NULL

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Date:   Tue,  5 Jul 2022 13:57:32 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, linux-cifs@...r.kernel.org,
        Ronnie Sahlberg <lsahlber@...hat.com>,
        Hyunchul Lee <hyc.lee@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Namjae Jeon <linkinjeon@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Steve French <stfrench@...rosoft.com>
Subject: [PATCH 5.18 006/102] ksmbd: use vfs_llseek instead of dereferencing NULL

From: Jason A. Donenfeld <Jason@...c4.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@...r.kernel.org
Cc: linux-cifs@...r.kernel.org
Cc: Ronnie Sahlberg <lsahlber@...hat.com>
Cc: Hyunchul Lee <hyc.lee@...il.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Reviewed-by: Namjae Jeon <linkinjeon@...nel.org>
Acked-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/ksmbd/vfs.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/ksmbd/vfs.c
+++ b/fs/ksmbd/vfs.c
@@ -1048,7 +1048,7 @@ 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;
@@ -1058,7 +1058,7 @@ 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;