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authorXu Yu <xuyu@linux.alibaba.com>2019-04-03 18:39:15 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-04-20 09:15:09 +0200
commit12462c88e6e281cd136ae7c93e85fadfcf20722f (patch)
tree88c6d9089b9148f33e4f668035513e03d8ad1246
parent0ed998d17cd421da18334745af7aee246abe4c70 (diff)
bpf: do not restore dst_reg when cur_state is freed
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>
-rw-r--r--kernel/bpf/verifier.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ec949a4a7d89..87b1293f20d6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2118,7 +2118,7 @@ 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;
}