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bpf: fix matching of data/data_end in verifier

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The ctx structure passed into bpf programs is different depending on bpf
program type. The verifier incorrectly marked ctx->data and ctx->data_end
access based on ctx offset only. That caused loads in tracing programs
int bpf_prog(struct pt_regs *ctx) { .. ctx->ax .. }
to be incorrectly marked as PTR_TO_PACKET which later caused verifier
to reject the program that was actually valid in tracing context.
Fix this by doing program type specific matching of ctx offsets.

Fixes: 969bf05eb3 ("bpf: direct packet access")
Reported-by: Sasha Goldshtein <goldshtn@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov 2016-06-15 18:25:38 -07:00 • committed by David S. Miller
parent e582615ad3
commit 19de99f70b
4 changed files with 52 additions and 39 deletions
Download patch file Download diff file Expand all files Collapse all files

16
net/core/filter.c
View file

@ -2085,7 +2085,8 @@ static bool __is_valid_access(int off, int size, enum bpf_access_type type)
}
static bool sk_filter_is_valid_access(int off, int size,
enum bpf_access_type type)
enum bpf_access_type type,
enum bpf_reg_type *reg_type)
{
switch (off) {
case offsetof(struct __sk_buff, tc_classid):
@ -2108,7 +2109,8 @@ static bool sk_filter_is_valid_access(int off, int size,
}
static bool tc_cls_act_is_valid_access(int off, int size,
enum bpf_access_type type)
enum bpf_access_type type,
enum bpf_reg_type *reg_type)
{
if (type == BPF_WRITE) {
switch (off) {
@ -2123,6 +2125,16 @@ static bool tc_cls_act_is_valid_access(int off, int size,
return false;
}
}
switch (off) {
case offsetof(struct __sk_buff, data):
*reg_type = PTR_TO_PACKET;
break;
case offsetof(struct __sk_buff, data_end):
*reg_type = PTR_TO_PACKET_END;
break;
}
return __is_valid_access(off, size, type);
}