5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Zijian Zhang <zijianzhang@xxxxxxxxxxxxx>
[ 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@xxxxxxxxxxxxx>
Reviewed-by: John Fastabend <john.fastabend@xxxxxxxxx>
Link: https://lore.kernel.org/r/20241106222520.527076-8-zijianzhang@xxxxxxxxxxxxx
Signed-off-by: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/core/filter.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index c5d15fceee6da..8b51f57aaa251 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2883,8 +2883,10 @@ static const struct bpf_func_proto bpf_msg_push_data_proto = {
static void sk_msg_shift_left(struct sk_msg *msg, int i)
{
+ struct scatterlist *sge = sk_msg_elem(msg, i);
int prev;
+ put_page(sg_page(sge));
do {
prev = i;
sk_msg_iter_var_next(i);
@@ -2921,6 +2923,9 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
if (unlikely(flags))
return -EINVAL;
+ if (unlikely(len == 0))
+ return 0;
+
/* First find the starting scatterlist element */
i = msg->sg.start;
do {
@@ -2933,7 +2938,7 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
} while (i != msg->sg.end);
/* 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;
space = MAX_MSG_FRAGS - sk_msg_elem_used(msg);
@@ -2962,12 +2967,12 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
*/
if (start != offset) {
struct scatterlist *nsge, *sge = sk_msg_elem(msg, i);
- int a = start;
+ int a = start - offset;
int b = sge->length - pop - a;
sk_msg_iter_var_next(i);
- if (pop < sge->length - a) {
+ if (b > 0) {
if (space) {
sge->length = a;
sk_msg_shift_right(msg, i);
@@ -2986,7 +2991,6 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
if (unlikely(!page))
return -ENOMEM;
- sge->length = a;
orig = sg_page(sge);
from = sg_virt(sge);
to = page_address(page);
@@ -2996,7 +3000,7 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
put_page(orig);
}
pop = 0;
- } else if (pop >= sge->length - a) {
+ } else {
pop -= (sge->length - a);
sge->length = a;
}
@@ -3030,7 +3034,6 @@ BPF_CALL_4(bpf_msg_pop_data, struct sk_msg *, msg, u32, start,
pop -= sge->length;
sk_msg_shift_left(msg, i);
}
- sk_msg_iter_var_next(i);
}
sk_mem_uncharge(msg->sk, len - pop);
--
2.43.0
