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 bpf-next] bpf: Remove bpf_lsm_file_mprotect from sleepable list.
Date: Mon, 31 Aug 2020 13:16:51 -0700 [thread overview]
Message-ID: <20200831201651.82447-1-alexei.starovoitov@gmail.com> (raw)
From: Alexei Starovoitov <ast@kernel.org>
Technically the bpf programs can sleep while attached to bpf_lsm_file_mprotect,
but such programs need to access user memory. So they're in might_fault()
category. Which means they cannot be called from file_mprotect lsm hook that
takes write lock on mm->mmap_lock.
Adjust the test accordingly.
Also add might_fault() to __bpf_prog_enter_sleepable() to catch such deadlocks early.
Reported-by: Yonghong Song <yhs@fb.com>
Fixes: 1e6c62a88215 ("bpf: Introduce sleepable BPF programs")
Fixes: e68a144547fc ("selftests/bpf: Add sleepable tests")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
kernel/bpf/trampoline.c | 1 +
kernel/bpf/verifier.c | 1 -
tools/testing/selftests/bpf/progs/lsm.c | 34 ++++++++++++-------------
3 files changed, 18 insertions(+), 18 deletions(-)
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index c2b76545153c..7dd523a7e32d 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -409,6 +409,7 @@ void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start)
void notrace __bpf_prog_enter_sleepable(void)
{
rcu_read_lock_trace();
+ might_fault();
}
void notrace __bpf_prog_exit_sleepable(void)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b4c22b5ce5a2..b4e9c56b8b32 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -11006,7 +11006,6 @@ static int check_attach_modify_return(struct bpf_prog *prog, unsigned long addr)
/* non exhaustive list of sleepable bpf_lsm_*() functions */
BTF_SET_START(btf_sleepable_lsm_hooks)
#ifdef CONFIG_BPF_LSM
-BTF_ID(func, bpf_lsm_file_mprotect)
BTF_ID(func, bpf_lsm_bprm_committed_creds)
#else
BTF_ID_UNUSED
diff --git a/tools/testing/selftests/bpf/progs/lsm.c b/tools/testing/selftests/bpf/progs/lsm.c
index 49fa6ca99755..ff4d343b94b5 100644
--- a/tools/testing/selftests/bpf/progs/lsm.c
+++ b/tools/testing/selftests/bpf/progs/lsm.c
@@ -36,14 +36,10 @@ int monitored_pid = 0;
int mprotect_count = 0;
int bprm_count = 0;
-SEC("lsm.s/file_mprotect")
+SEC("lsm/file_mprotect")
int BPF_PROG(test_int_hook, struct vm_area_struct *vma,
unsigned long reqprot, unsigned long prot, int ret)
{
- char args[64];
- __u32 key = 0;
- __u64 *value;
-
if (ret != 0)
return ret;
@@ -53,18 +49,6 @@ int BPF_PROG(test_int_hook, struct vm_area_struct *vma,
is_stack = (vma->vm_start <= vma->vm_mm->start_stack &&
vma->vm_end >= vma->vm_mm->start_stack);
- bpf_copy_from_user(args, sizeof(args), (void *)vma->vm_mm->arg_start);
-
- value = bpf_map_lookup_elem(&array, &key);
- if (value)
- *value = 0;
- value = bpf_map_lookup_elem(&hash, &key);
- if (value)
- *value = 0;
- value = bpf_map_lookup_elem(&lru_hash, &key);
- if (value)
- *value = 0;
-
if (is_stack && monitored_pid == pid) {
mprotect_count++;
ret = -EPERM;
@@ -77,10 +61,26 @@ SEC("lsm.s/bprm_committed_creds")
int BPF_PROG(test_void_hook, struct linux_binprm *bprm)
{
__u32 pid = bpf_get_current_pid_tgid() >> 32;
+ char args[64];
+ __u32 key = 0;
+ __u64 *value;
if (monitored_pid == pid)
bprm_count++;
+ bpf_copy_from_user(args, sizeof(args), (void *)bprm->vma->vm_mm->arg_start);
+ bpf_copy_from_user(args, sizeof(args), (void *)bprm->mm->arg_start);
+
+ value = bpf_map_lookup_elem(&array, &key);
+ if (value)
+ *value = 0;
+ value = bpf_map_lookup_elem(&hash, &key);
+ if (value)
+ *value = 0;
+ value = bpf_map_lookup_elem(&lru_hash, &key);
+ if (value)
+ *value = 0;
+
return 0;
}
SEC("lsm/task_free") /* lsm/ is ok, lsm.s/ fails */
--
2.23.0
next reply other threads:[~2020-08-31 20:16 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-31 20:16 Alexei Starovoitov [this message]
2020-08-31 21:25 ` [PATCH bpf-next] bpf: Remove bpf_lsm_file_mprotect from sleepable list Daniel Borkmann
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