linux-kernel - [PATCH 2/2] afs: Increase buffer size in afs_update_volume

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Date: Mon, 19 Feb 2024 14:39:03 +0000
From: David Howells <dhowells@...hat.com>
To: Christian Brauner <christian@...uner.io>
Cc: David Howells <dhowells@...hat.com>,
	Markus Suvanto <markus.suvanto@...il.com>,
	Marc Dionne <marc.dionne@...istor.com>,
	Daniil Dulov <d.dulov@...ddin.ru>,
	linux-afs@...ts.infradead.org,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] afs: Increase buffer size in afs_update_volume_status()

From: Daniil Dulov <d.dulov@...ddin.ru>

The max length of volume->vid value is 20 characters.
So increase idbuf[] size up to 24 to avoid overflow.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

[DH: Actually, it's 20 + NUL, so increase it to 24 and use snprintf()]

Fixes: d2ddc776a458 ("afs: Overhaul volume and server record caching and fileserver rotation")
Signed-off-by: Daniil Dulov <d.dulov@...ddin.ru>
Signed-off-by: David Howells <dhowells@...hat.com>
Link: https://lore.kernel.org/r/20240211150442.3416-1-d.dulov@aladdin.ru/ # v1
Link: https://lore.kernel.org/r/20240212083347.10742-1-d.dulov@aladdin.ru/ # v2
---
 fs/afs/volume.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/afs/volume.c b/fs/afs/volume.c
index 020ecd45e476..af3a3f57c1b3 100644
--- a/fs/afs/volume.c
+++ b/fs/afs/volume.c
@@ -353,7 +353,7 @@ static int afs_update_volume_status(struct afs_volume *volume, struct key *key)
 {
 	struct afs_server_list *new, *old, *discard;
 	struct afs_vldb_entry *vldb;
-	char idbuf[16];
+	char idbuf[24];
 	int ret, idsz;
 
 	_enter("");
@@ -361,7 +361,7 @@ static int afs_update_volume_status(struct afs_volume *volume, struct key *key)
 	/* We look up an ID by passing it as a decimal string in the
 	 * operation's name parameter.
 	 */
-	idsz = sprintf(idbuf, "%llu", volume->vid);
+	idsz = snprintf(idbuf, sizeof(idbuf), "%llu", volume->vid);
 
 	vldb = afs_vl_lookup_vldb(volume->cell, key, idbuf, idsz);
 	if (IS_ERR(vldb)) {