R0dn3yS/android_kernel_xiaomi_sm7250
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

bpf: Reject indirect var_off stack access in raw mode

Browse Source 
commit f2bcd05ec7b839ff826d2008506ad2d2dff46a59 upstream.

It's hard to guarantee that whole memory is marked as initialized on
helper return if uninitialized stack is accessed with variable offset
since specific bounds are unknown to verifier. This may cause
uninitialized stack leaking.

Reject such an access in check_stack_boundary to prevent possible
leaking.

There are no known use-cases for indirect uninitialized stack access
with variable offset so it shouldn't break anything.

Fixes: 2011fccfb61b ("bpf: Support variable offset stack access from helpers")
Reported-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Andrey Ignatov 2021-09-13 18:35:28 +03:00 committed by Greg Kroah-Hartman
parent caee4103f0
commit 148339cb18
1 changed files with 9 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
kernel/bpf/verifier.c
View File

@ -1811,6 +1811,15 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
if (err)
return err;
} else {
/* Only initialized buffer on stack is allowed to be accessed
* with variable offset. With uninitialized buffer it's hard to
* guarantee that whole memory is marked as initialized on
* helper return since specific bounds are unknown what may
* cause uninitialized stack leaking.
*/
if (meta && meta->raw_mode)
meta = NULL;
min_off = reg->smin_value + reg->off;
max_off = reg->umax_value + reg->off;
err = __check_stack_boundary(env, regno, min_off, access_size,