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bpf, sockmap: Several fixes to bpf_msg_pop_data

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[ Upstream commit 5d609ba262475db450ba69b8e8a557bd768ac07a ]

Several fixes to bpf_msg_pop_data,
1. In sk_msg_shift_left, we should put_page
2. if (len == 0), return early is better
3. pop the entire sk_msg (last == msg->sg.size) should be supported
4. Fix for the value of variable "a"
5. In sk_msg_shift_left, after shifting, i has already pointed to the next
element. Addtional sk_msg_iter_var_next may result in BUG.

Fixes: 7246d8ed4dcc ("bpf: helper to pop data from messages")
Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20241106222520.527076-8-zijianzhang@bytedance.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Zijian Zhang 2024-11-06 22:25:19 +00:00 committed by Greg Kroah-Hartman
parent cadfa4d23f
commit f58d3aa457
1 changed files with 9 additions and 6 deletions
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15
net/core/filter.c
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@ -2894,8 +2894,10 @@ static const struct bpf_func_proto bpf_msg_push_data_proto = {
static void sk_msg_shift_left(struct sk_msg *msg, int i) static void sk_msg_shift_left(struct sk_msg *msg, int i)
{ {
struct scatterlist *sge = sk_msg_elem(msg, i);
int prev; int prev;
put_page(sg_page(sge));
do { do {
prev = i; prev = i;
sk_msg_iter_var_next(i); sk_msg_iter_var_next(i);
@ -2932,6 +2934,9 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
if (unlikely(flags)) if (unlikely(flags))
return -EINVAL; return -EINVAL;
if (unlikely(len == 0))
return 0;
/* First find the starting scatterlist element */ /* First find the starting scatterlist element */
i = msg->sg.start; i = msg->sg.start;
do { do {
@ -2944,7 +2949,7 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
} while (i != msg->sg.end); } while (i != msg->sg.end);
/* Bounds checks: start and pop must be inside message */ /* Bounds checks: start and pop must be inside message */
if (start >= offset + l || last >= msg->sg.size) if (start >= offset + l || last > msg->sg.size)
return -EINVAL; return -EINVAL;
space = MAX_MSG_FRAGS - sk_msg_elem_used(msg); space = MAX_MSG_FRAGS - sk_msg_elem_used(msg);
@ -2973,12 +2978,12 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
*/ */
if (start != offset) { if (start != offset) {
struct scatterlist *nsge, *sge = sk_msg_elem(msg, i); struct scatterlist *nsge, *sge = sk_msg_elem(msg, i);
int a = start; int a = start - offset;
int b = sge->length - pop - a; int b = sge->length - pop - a;
sk_msg_iter_var_next(i); sk_msg_iter_var_next(i);
if (pop < sge->length - a) { if (b > 0) {
if (space) { if (space) {
sge->length = a; sge->length = a;
sk_msg_shift_right(msg, i); sk_msg_shift_right(msg, i);
@ -2997,7 +3002,6 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
if (unlikely(!page)) if (unlikely(!page))
return -ENOMEM; return -ENOMEM;
sge->length = a;
orig = sg_page(sge); orig = sg_page(sge);
from = sg_virt(sge); from = sg_virt(sge);
to = page_address(page); to = page_address(page);
@ -3007,7 +3011,7 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
put_page(orig); put_page(orig);
} }
pop = 0; pop = 0;
} else if (pop >= sge->length - a) { } else {
pop -= (sge->length - a); pop -= (sge->length - a);
sge->length = a; sge->length = a;
} }
@ -3041,7 +3045,6 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
pop -= sge->length; pop -= sge->length;
sk_msg_shift_left(msg, i); sk_msg_shift_left(msg, i);
} }
sk_msg_iter_var_next(i);
} }
sk_mem_uncharge(msg->sk, len - pop); sk_mem_uncharge(msg->sk, len - pop);