bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: davem@davemloft.net
Cc: daniel@iogearbox.net, netdev@vger.kernel.org,
	bpf@vger.kernel.org, kernel-team@fb.com
Subject: [PATCH v2 bpf-next 1/4] bpf: Fix use-after-free in fmod_ret check
Date: Thu, 28 May 2020 21:38:36 -0700	[thread overview]
Message-ID: <20200529043839.15824-2-alexei.starovoitov@gmail.com> (raw)
In-Reply-To: <20200529043839.15824-1-alexei.starovoitov@gmail.com>

From: Alexei Starovoitov <ast@kernel.org>

Fix the following issue:
[  436.749342] BUG: KASAN: use-after-free in bpf_trampoline_put+0x39/0x2a0
[  436.749995] Write of size 4 at addr ffff8881ef38b8a0 by task kworker/3:5/2243
[  436.750712]
[  436.752677] Workqueue: events bpf_prog_free_deferred
[  436.753183] Call Trace:
[  436.756483]  bpf_trampoline_put+0x39/0x2a0
[  436.756904]  bpf_prog_free_deferred+0x16d/0x3d0
[  436.757377]  process_one_work+0x94a/0x15b0
[  436.761969]
[  436.762130] Allocated by task 2529:
[  436.763323]  bpf_trampoline_lookup+0x136/0x540
[  436.763776]  bpf_check+0x2872/0xa0a8
[  436.764144]  bpf_prog_load+0xb6f/0x1350
[  436.764539]  __do_sys_bpf+0x16d7/0x3720
[  436.765825]
[  436.765988] Freed by task 2529:
[  436.767084]  kfree+0xc6/0x280
[  436.767397]  bpf_trampoline_put+0x1fd/0x2a0
[  436.767826]  bpf_check+0x6832/0xa0a8
[  436.768197]  bpf_prog_load+0xb6f/0x1350
[  436.768594]  __do_sys_bpf+0x16d7/0x3720

prog->aux->trampoline = tr should be set only when prog is valid.
Otherwise prog freeing will try to put trampoline via prog->aux->trampoline,
but it may not point to a valid trampoline.

Fixes: 6ba43b761c41 ("bpf: Attachment verification for BPF_MODIFY_RETURN")
Acked-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 kernel/bpf/verifier.c | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d2e27dba4ac6..8cf8dae86f00 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10522,22 +10522,13 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
 }
 #define SECURITY_PREFIX "security_"
 
-static int check_attach_modify_return(struct bpf_verifier_env *env)
+static int check_attach_modify_return(struct bpf_prog *prog, unsigned long addr)
 {
-	struct bpf_prog *prog = env->prog;
-	unsigned long addr = (unsigned long) prog->aux->trampoline->func.addr;
-
-	/* This is expected to be cleaned up in the future with the KRSI effort
-	 * introducing the LSM_HOOK macro for cleaning up lsm_hooks.h.
-	 */
 	if (within_error_injection_list(addr) ||
 	    !strncmp(SECURITY_PREFIX, prog->aux->attach_func_name,
 		     sizeof(SECURITY_PREFIX) - 1))
 		return 0;
 
-	verbose(env, "fmod_ret attach_btf_id %u (%s) is not modifiable\n",
-		prog->aux->attach_btf_id, prog->aux->attach_func_name);
-
 	return -EINVAL;
 }
 
@@ -10765,11 +10756,18 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 				goto out;
 			}
 		}
+
+		if (prog->expected_attach_type == BPF_MODIFY_RETURN) {
+			ret = check_attach_modify_return(prog, addr);
+			if (ret)
+				verbose(env, "%s() is not modifiable\n",
+					prog->aux->attach_func_name);
+		}
+
+		if (ret)
+			goto out;
 		tr->func.addr = (void *)addr;
 		prog->aux->trampoline = tr;
-
-		if (prog->expected_attach_type == BPF_MODIFY_RETURN)
-			ret = check_attach_modify_return(env);
 out:
 		mutex_unlock(&tr->mutex);
 		if (ret)
-- 
2.23.0


  reply	other threads:[~2020-05-29  4:38 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-29  4:38 [PATCH v2 bpf-next 0/4] bpf: Introduce minimal support for sleepable progs Alexei Starovoitov
2020-05-29  4:38 ` Alexei Starovoitov [this message]
2020-05-29  4:38 ` [PATCH v2 bpf-next 2/4] bpf: Introduce sleepable BPF programs Alexei Starovoitov
2020-05-29  8:25   ` Andrii Nakryiko
2020-05-29 20:12     ` Alexei Starovoitov
2020-05-29 20:38       ` Andrii Nakryiko
2020-05-29 20:52         ` Alexei Starovoitov
2020-05-31  2:19   ` kbuild test robot
2020-05-31  4:33   ` kbuild test robot
2020-05-29  4:38 ` [PATCH v2 bpf-next 3/4] libbpf: support sleepable progs Alexei Starovoitov
2020-05-29  4:38 ` [PATCH v2 bpf-next 4/4] selftests/bpf: basic sleepable tests Alexei Starovoitov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200529043839.15824-2-alexei.starovoitov@gmail.com \
    --to=alexei.starovoitov@gmail.com \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=davem@davemloft.net \
    --cc=kernel-team@fb.com \
    --cc=netdev@vger.kernel.org \
    --subject='Re: [PATCH v2 bpf-next 1/4] bpf: Fix use-after-free in fmod_ret check' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).