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bpf: Fix a data-race around bpf_jit_limit.

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While reading bpf_jit_limit, it can be changed concurrently via sysctl,
WRITE_ONCE() in __do_proc_doulongvec_minmax(). The size of bpf_jit_limit
is long, so we need to add a paired READ_ONCE() to avoid load-tearing.

Fixes: ede95a63b5e8 ("bpf: add bpf_jit_limit knob to restrict unpriv allocations")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220823215804.2177-1-kuniyu@amazon.com
This commit is contained in:
Kuniyuki Iwashima 2022-08-23 14:58:04 -07:00 committed by Daniel Borkmann
parent 7d6620f107
commit 0947ae1121
1 changed files with 1 additions and 1 deletions
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2
kernel/bpf/core.c
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@ -971,7 +971,7 @@ pure_initcall(bpf_jit_charge_init);
int bpf_jit_charge_modmem(u32 size) int bpf_jit_charge_modmem(u32 size)
{ {
if (atomic_long_add_return(size, &bpf_jit_current) > bpf_jit_limit) { if (atomic_long_add_return(size, &bpf_jit_current) > READ_ONCE(bpf_jit_limit)) {
if (!bpf_capable()) { if (!bpf_capable()) {
atomic_long_sub(size, &bpf_jit_current); atomic_long_sub(size, &bpf_jit_current);
return -EPERM; return -EPERM;