[PATCH] net: sched: fix warning in tcindex_alloc_perfect_hash

Syzbot reported warning in tcindex_alloc_perfect_hash. The problem
was in too big cp->hash, which triggers warning in kmalloc. Since
cp->hash comes from userspace, there is no need to warn if value
is not correct

Fixes: b9a24bb76bf6 ("net_sched: properly handle failure case of tcf_exts_init()")
Reported-and-tested-by: syzbot+1071ad60cd7df39fdadb@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <redacted>
---
 net/sched/cls_tcindex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c
index c4007b9cd16d..5b274534264c 100644
--- a/net/sched/cls_tcindex.c
+++ b/net/sched/cls_tcindex.c

@@ -304,7 +304,7 @@ static int tcindex_alloc_perfect_hash(struct net *net, struct tcindex_data *cp)
 	int i, err = 0;
 
 	cp->perfect = kcalloc(cp->hash, sizeof(struct tcindex_filter_result),
-			      GFP_KERNEL);
+			      GFP_KERNEL | __GFP_NOWARN);
 	if (!cp->perfect)
 		return -ENOMEM;
 

-- 
2.32.0

On Fri, Jun 25, 2021 at 1:23 PM Pavel Skripkin [off-list ref] wrote:

Syzbot reported warning in tcindex_alloc_perfect_hash. The problem
was in too big cp->hash, which triggers warning in kmalloc. Since
cp->hash comes from userspace, there is no need to warn if value
is not correct

Fixes: b9a24bb76bf6 ("net_sched: properly handle failure case of tcf_exts_init()")
Reported-and-tested-by: syzbot+1071ad60cd7df39fdadb@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <redacted>

Looks reasonable.

Acked-by: Cong Wang <redacted>

Thanks.

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Fri, 25 Jun 2021 23:23:48 +0300 you wrote:

Syzbot reported warning in tcindex_alloc_perfect_hash. The problem
was in too big cp->hash, which triggers warning in kmalloc. Since
cp->hash comes from userspace, there is no need to warn if value
is not correct

Fixes: b9a24bb76bf6 ("net_sched: properly handle failure case of tcf_exts_init()")
Reported-and-tested-by: syzbot+1071ad60cd7df39fdadb@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <redacted>

[...]

Here is the summary with links:
  - net: sched: fix warning in tcindex_alloc_perfect_hash
    https://git.kernel.org/netdev/net/c/3f2db250099f

You are awesome, thank you!
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