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libbpf: Check the validity of size in user_ring_buffer__reserve()

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The top two bits of size are used as busy and discard flags, so reject
the reservation that has any of these special bits in the size. With the
addition of validity check, these is also no need to check whether or
not total_size is overflowed.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221116072351.1168938-5-houtao@huaweicloud.com
This commit is contained in:
Hou Tao 2022-11-16 15:23:51 +08:00 committed by Andrii Nakryiko
parent 64176bff24
commit 05c1558bfc
1 changed files with 4 additions and 0 deletions
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4
tools/lib/bpf/ringbuf.c
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@ -486,6 +486,10 @@ void *user_ring_buffer__reserve(struct user_ring_buffer *rb, __u32 size)
__u64 cons_pos, prod_pos;
struct ringbuf_hdr *hdr;
/* The top two bits are used as special flags */
if (size & (BPF_RINGBUF_BUSY_BIT | BPF_RINGBUF_DISCARD_BIT))
return errno = E2BIG, NULL;
/* Synchronizes with smp_store_release() in __bpf_user_ringbuf_peek() in
* the kernel.
*/