6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Zijian Zhang zijianzhang@bytedance.com
[ 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 --- 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 b4ed0d9177818..5174f4d48647f 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -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) { + struct scatterlist *sge = sk_msg_elem(msg, i); int prev;
+ put_page(sg_page(sge)); do { prev = 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)) return -EINVAL;
+ if (unlikely(len == 0)) + return 0; + /* First find the starting scatterlist element */ i = msg->sg.start; do { @@ -2944,7 +2949,7 @@ 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); @@ -2973,12 +2978,12 @@ 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); @@ -2997,7 +3002,6 @@ 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); @@ -3007,7 +3011,7 @@ 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; } @@ -3041,7 +3045,6 @@ 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);