netdev - [PATCH bpf 1/4] xsk: do not write NULL in SW ring at allocation failure

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 28 Mar 2022 16:21:20 +0200
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net
Cc:     netdev@...r.kernel.org, magnus.karlsson@...el.com,
        alexandr.lobakin@...el.com, bjorn@...nel.org
Subject: [PATCH bpf 1/4] xsk: do not write NULL in SW ring at allocation failure

From: Magnus Karlsson <magnus.karlsson@...el.com>

For the case when xp_alloc_batch() is used but the batched allocation
cannot be used, there is a slow path that uses the non-batched
xp_alloc(). When it fails to allocate an entry, it returns NULL. The
current code wrote this NULL into the entry of the provided results
array (pointer to the driver SW ring usually) and returned. This might
not be what the driver expects and to make things simpler, just write
successfully allocated xdp_buffs into the SW ring,. The driver might
have information in there that is still important after an allocation
failure.

Note that at this point in time, there are no drivers using
xp_alloc_batch() that could trigger this slow path. But one might get
added.

Fixes: 47e4075df300 ("xsk: Batched buffer allocation for the pool")
Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
---
 net/xdp/xsk_buff_pool.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index b34fca6ada86..af040ffa14ff 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -591,9 +591,13 @@ u32 xp_alloc_batch(struct xsk_buff_pool *pool, struct xdp_buff **xdp, u32 max)
 	u32 nb_entries1 = 0, nb_entries2;

 	if (unlikely(pool->dma_need_sync)) {
+		struct xdp_buff *buff;
+
 		/* Slow path */
-		*xdp = xp_alloc(pool);
-		return !!*xdp;
+		buff = xp_alloc(pool);
+		if (buff)
+			*xdp = buff;
+		return !!buff;
 	}

 	if (unlikely(pool->free_list_cnt)) {
-- 
2.27.0