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Subject[PATCH 4.4 073/266] bpf: reject wrong sized filters earlier
Date
From: Daniel Borkmann <daniel@iogearbox.net>

commit f7bd9e36ee4a4ce38e1cddd7effe6c0d9943285b upstream.

Add a bpf_check_basics_ok() and reject filters that are of invalid
size much earlier, so we don't do any useless work such as invoking
bpf_prog_alloc(). Currently, rejection happens in bpf_check_classic()
only, but it's really unnecessarily late and they should be rejected
at earliest point. While at it, also clean up one bpf_prog_size() to
make it consistent with the remaining invocations.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zubin Mithra <zsm@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/filter.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)

--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -742,6 +742,17 @@ static bool chk_code_allowed(u16 code_to
return codes[code_to_probe];
}

+static bool bpf_check_basics_ok(const struct sock_filter *filter,
+ unsigned int flen)
+{
+ if (filter == NULL)
+ return false;
+ if (flen == 0 || flen > BPF_MAXINSNS)
+ return false;
+
+ return true;
+}
+
/**
* bpf_check_classic - verify socket filter code
* @filter: filter to verify
@@ -762,9 +773,6 @@ static int bpf_check_classic(const struc
bool anc_found;
int pc;

- if (flen == 0 || flen > BPF_MAXINSNS)
- return -EINVAL;
-
/* Check the filter code now */
for (pc = 0; pc < flen; pc++) {
const struct sock_filter *ftest = &filter[pc];
@@ -1057,7 +1065,7 @@ int bpf_prog_create(struct bpf_prog **pf
struct bpf_prog *fp;

/* Make sure new filter is there and in the right amounts. */
- if (fprog->filter == NULL)
+ if (!bpf_check_basics_ok(fprog->filter, fprog->len))
return -EINVAL;

fp = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
@@ -1104,7 +1112,7 @@ int bpf_prog_create_from_user(struct bpf
int err;

/* Make sure new filter is there and in the right amounts. */
- if (fprog->filter == NULL)
+ if (!bpf_check_basics_ok(fprog->filter, fprog->len))
return -EINVAL;

fp = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
@@ -1184,7 +1192,6 @@ int __sk_attach_filter(struct sock_fprog
bool locked)
{
unsigned int fsize = bpf_classic_proglen(fprog);
- unsigned int bpf_fsize = bpf_prog_size(fprog->len);
struct bpf_prog *prog;
int err;

@@ -1192,10 +1199,10 @@ int __sk_attach_filter(struct sock_fprog
return -EPERM;

/* Make sure new filter is there and in the right amounts. */
- if (fprog->filter == NULL)
+ if (!bpf_check_basics_ok(fprog->filter, fprog->len))
return -EINVAL;

- prog = bpf_prog_alloc(bpf_fsize, 0);
+ prog = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
if (!prog)
return -ENOMEM;


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