| Message ID | 20200831201651.82447-1-alexei.starovoitov@gmail.com |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [bpf-next] bpf: Remove bpf_lsm_file_mprotect from sleepable list. | expand |
On 8/31/20 10:16 PM, Alexei Starovoitov wrote: > 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(); Makes sense, was wondering about a __might_sleep() but that will cover it internally too. Applied, thanks! > } > > void notrace __bpf_prog_exit_sleepable(void)
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 */