linux-kernel - [PATCH] bpf: Fix excessive memory allocation in stack_map

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Message-Id: <20220608142538.3215426-1-ytcoode@gmail.com>
Date:   Wed,  8 Jun 2022 22:25:38 +0800
From:   Yuntao Wang <ytcoode@...il.com>
To:     pavel@...x.de
Cc:     daniel@...earbox.net, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, sashal@...nel.org,
        stable@...r.kernel.org, ytcoode@...il.com
Subject: [PATCH] bpf: Fix excessive memory allocation in stack_map_alloc()

The 'n_buckets * (value_size + sizeof(struct stack_map_bucket))' part of
the allocated memory for 'smap' is never used, get rid of it.

Fixes: b936ca643ade ("bpf: rework memlock-based memory accounting for maps")
Signed-off-by: Yuntao Wang <ytcoode@...il.com>
Link: https://lore.kernel.org/bpf/20220407130423.798386-1-ytcoode@gmail.com
---
This is the modified version for 5.10, the original patch is:

[ Upstream commit b45043192b3e481304062938a6561da2ceea46a6 ]

It would be better if the new patch can be reviewed by someone else.

 kernel/bpf/stackmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 4575d2d60cb1..54fdcb78ad19 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -121,8 +121,8 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
 		return ERR_PTR(-E2BIG);
 
 	cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
-	cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
-	err = bpf_map_charge_init(&mem, cost);
+	err = bpf_map_charge_init(&mem, cost + n_buckets *
+				  (value_size + sizeof(struct stack_map_bucket)));
 	if (err)
 		return ERR_PTR(err);
 
-- 
2.36.0