android/android_kernel_samsung_sm8650
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

bpf: Add sanity check for upper ptr_limit

Browse Source 
Given we know the max possible value of ptr_limit at the time of retrieving
the latter, add basic assertions, so that the verifier can bail out if
anything looks odd and reject the program. Nothing triggered this so far,
but it also does not hurt to have these.

Signed-off-by: Piotr Krysiuk <piotras@gmail.com>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Piotr Krysiuk 2021-03-16 09:47:02 +01:00 committed by Daniel Borkmann
parent b5871dca25
commit 1b1597e64e
1 changed files with 8 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
kernel/bpf/verifier.c
View File

@ -5861,10 +5861,14 @@ static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
{
bool mask_to_left = (opcode == BPF_ADD && off_is_neg) ||
(opcode == BPF_SUB && !off_is_neg);
u32 off;
u32 off, max;
switch (ptr_reg->type) {
case PTR_TO_STACK:
/* Offset 0 is out-of-bounds, but acceptable start for the
* left direction, see BPF_REG_FP.
*/
max = MAX_BPF_STACK + mask_to_left;
/* Indirect variable offset stack access is prohibited in
* unprivileged mode so it's not handled here.
*/
@ -5873,15 +5877,16 @@ static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
*ptr_limit = MAX_BPF_STACK + off;
else
*ptr_limit = -off - 1;
return 0;
return *ptr_limit >= max ? -ERANGE : 0;
case PTR_TO_MAP_VALUE:
max = ptr_reg->map_ptr->value_size;
if (mask_to_left) {
*ptr_limit = ptr_reg->umax_value + ptr_reg->off;
} else {
off = ptr_reg->smin_value + ptr_reg->off;
*ptr_limit = ptr_reg->map_ptr->value_size - off - 1;
}
return 0;
return *ptr_limit >= max ? -ERANGE : 0;
default:
return -EINVAL;
}