bpf: Fix excessive memory allocation in stack_map_alloc()

BugLink: https://bugs.launchpad.net/bugs/1981862
commit b45043192b3e481304062938a6561da2ceea46a6 upstream.

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

[ Note, Daniel:

Commit b936ca643ade ("bpf: rework memlock-based memory accounting for maps")
moved `cost += n_buckets * (value_size + sizeof(struct stack_map_bucket))`
up and therefore before the bpf_map_area_alloc() allocation, sigh. In a later
step commit c85d69135a91 ("bpf: move memory size checks to bpf_map_charge_init()"),
and the overflow checks of `cost >= U32_MAX - PAGE_SIZE` moved into
bpf_map_charge_init(). And then 370868107bf6 ("bpf: Eliminate rlimit-based
memory accounting for stackmap maps") finally removed the bpf_map_charge_init().
Anyway, the original code did the allocation same way as /after/ this fix. ]

Fixes: b936ca643ade ("bpf: rework memlock-based memory accounting for maps")
Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220407130423.798386-1-ytcoode@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index fc0f77f91224bfaa316b3e9e30b12b55e4b6d8ca..7efae3af62017c8733b78b667e4b0d77a17f883f 100644 (file)
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -119,7 +119,6 @@ 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));
        smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
        if (!smap)
                return ERR_PTR(-ENOMEM);