lkml.org 
[lkml]   [2019]   [Apr]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 5.0 145/146] bpf: do not restore dst_reg when cur_state is freed
Date
5.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xu Yu <xuyu@linux.alibaba.com>

commit 0803278b0b4d8eeb2b461fb698785df65a725d9e upstream.

Syzkaller hit 'KASAN: use-after-free Write in sanitize_ptr_alu' bug.

Call trace:

dump_stack+0xbf/0x12e
print_address_description+0x6a/0x280
kasan_report+0x237/0x360
sanitize_ptr_alu+0x85a/0x8d0
adjust_ptr_min_max_vals+0x8f2/0x1ca0
adjust_reg_min_max_vals+0x8ed/0x22e0
do_check+0x1ca6/0x5d00
bpf_check+0x9ca/0x2570
bpf_prog_load+0xc91/0x1030
__se_sys_bpf+0x61e/0x1f00
do_syscall_64+0xc8/0x550
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Fault injection trace:

 kfree+0xea/0x290
 free_func_state+0x4a/0x60
 free_verifier_state+0x61/0xe0
 push_stack+0x216/0x2f0 <- inject failslab
 sanitize_ptr_alu+0x2b1/0x8d0
 adjust_ptr_min_max_vals+0x8f2/0x1ca0
 adjust_reg_min_max_vals+0x8ed/0x22e0
 do_check+0x1ca6/0x5d00
 bpf_check+0x9ca/0x2570
 bpf_prog_load+0xc91/0x1030
 __se_sys_bpf+0x61e/0x1f00
 do_syscall_64+0xc8/0x550
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

When kzalloc() fails in push_stack(), free_verifier_state() will free
current verifier state. As push_stack() returns, dst_reg was restored
if ptr_is_dst_reg is false. However, as member of the cur_state,
dst_reg is also freed, and error occurs when dereferencing dst_reg.
Simply fix it by testing ret of push_stack() before restoring dst_reg.

Fixes: 979d63d50c0c ("bpf: prevent out of bounds speculation on pointer arithmetic")
Signed-off-by: Xu Yu <xuyu@linux.alibaba.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/bpf/verifier.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3187,7 +3187,7 @@ do_sim:
*dst_reg = *ptr_reg;
}
ret = push_stack(env, env->insn_idx + 1, env->insn_idx, true);
- if (!ptr_is_dst_reg)
+ if (!ptr_is_dst_reg && ret)
*dst_reg = tmp;
return !ret ? -EFAULT : 0;
}

\
 
 \ /
  Last update: 2019-04-01 20:07    [W:0.352 / U:4.248 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site