Patch "block/rnbd-srv: Check for unlikely string overflow" has been added to the 6.6-stable tree

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This is a note to let you know that I've just added the patch titled

    block/rnbd-srv: Check for unlikely string overflow

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     block-rnbd-srv-check-for-unlikely-string-overflow.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 35e711459b42f75cd4882c1c8bd6cb3025a2151e
Author: Kees Cook <keescook@xxxxxxxxxxxx>
Date:   Tue Dec 12 13:47:42 2023 -0800

    block/rnbd-srv: Check for unlikely string overflow
    
    [ Upstream commit 9e4bf6a08d1e127bcc4bd72557f2dfafc6bc7f41 ]
    
    Since "dev_search_path" can technically be as large as PATH_MAX,
    there was a risk of truncation when copying it and a second string
    into "full_path" since it was also PATH_MAX sized. The W=1 builds were
    reporting this warning:
    
    drivers/block/rnbd/rnbd-srv.c: In function 'process_msg_open.isra':
    drivers/block/rnbd/rnbd-srv.c:616:51: warning: '%s' directive output may be truncated writing up to 254 bytes into a region of size between 0 and 4095 [-Wformat-truncation=]
      616 |                 snprintf(full_path, PATH_MAX, "%s/%s",
          |                                                   ^~
    In function 'rnbd_srv_get_full_path',
        inlined from 'process_msg_open.isra' at drivers/block/rnbd/rnbd-srv.c:721:14: drivers/block/rnbd/rnbd-srv.c:616:17: note: 'snprintf' output between 2 and 4351 bytes into a destination of size 4096
      616 |                 snprintf(full_path, PATH_MAX, "%s/%s",
          |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      617 |                          dev_search_path, dev_name);
          |                          ~~~~~~~~~~~~~~~~~~~~~~~~~~
    
    To fix this, unconditionally check for truncation (as was already done
    for the case where "%SESSNAME%" was present).
    
    Reported-by: kernel test robot <lkp@xxxxxxxxx>
    Closes: https://lore.kernel.org/oe-kbuild-all/202312100355.lHoJPgKy-lkp@xxxxxxxxx/
    Cc: Md. Haris Iqbal <haris.iqbal@xxxxxxxxx>
    Cc: Jack Wang <jinpu.wang@xxxxxxxxx>
    Cc: Jens Axboe <axboe@xxxxxxxxx>
    Cc:  <linux-block@xxxxxxxxxxxxxxx>
    Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
    Acked-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxx>
    Acked-by: Jack Wang <jinpu.wang@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20231212214738.work.169-kees@xxxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/block/rnbd/rnbd-srv.c b/drivers/block/rnbd/rnbd-srv.c
index c186df0ec641..b67e39a34010 100644
--- a/drivers/block/rnbd/rnbd-srv.c
+++ b/drivers/block/rnbd/rnbd-srv.c
@@ -585,6 +585,7 @@ static char *rnbd_srv_get_full_path(struct rnbd_srv_session *srv_sess,
 {
 	char *full_path;
 	char *a, *b;
+	int len;
 
 	full_path = kmalloc(PATH_MAX, GFP_KERNEL);
 	if (!full_path)
@@ -596,19 +597,19 @@ static char *rnbd_srv_get_full_path(struct rnbd_srv_session *srv_sess,
 	 */
 	a = strnstr(dev_search_path, "%SESSNAME%", sizeof(dev_search_path));
 	if (a) {
-		int len = a - dev_search_path;
+		len = a - dev_search_path;
 
 		len = snprintf(full_path, PATH_MAX, "%.*s/%s/%s", len,
 			       dev_search_path, srv_sess->sessname, dev_name);
-		if (len >= PATH_MAX) {
-			pr_err("Too long path: %s, %s, %s\n",
-			       dev_search_path, srv_sess->sessname, dev_name);
-			kfree(full_path);
-			return ERR_PTR(-EINVAL);
-		}
 	} else {
-		snprintf(full_path, PATH_MAX, "%s/%s",
-			 dev_search_path, dev_name);
+		len = snprintf(full_path, PATH_MAX, "%s/%s",
+			       dev_search_path, dev_name);
+	}
+	if (len >= PATH_MAX) {
+		pr_err("Too long path: %s, %s, %s\n",
+		       dev_search_path, srv_sess->sessname, dev_name);
+		kfree(full_path);
+		return ERR_PTR(-EINVAL);
 	}
 
 	/* eliminitate duplicated slashes */




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