diff options
| author | Aditya Sharma <adi.sharma@zohomail.in> | 2026-10-01 12:54:48 +0530 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2026-10-24 04:00:57 +0000 |
| commit | 93bd472336ac2424f5f3cf05cbb24e02242343b7 (patch) | |
| tree | 7ff5e659fc0e1686e901e263d17226243594de0f /kernel/trace | |
| parent | b93cf2c8a0552b544e90e25802e4bf989987d29d (diff) | |
bpf: Remove nmi_uaccess_okay() check in bpf_send_signal_common()
nmi_uaccess_okay() takes no task argument and is a statement about
current. When commit 6280cf718db0 ("bpf: Implement bpf_send_signal_task()
kfunc") made the PF_KTHREAD/PF_EXITING and is_global_init() test the
supplied task, nmi_uaccess_okay() was left testing current.
As a result bpf_send_signal_task() returns -EPERM whenever the
calling context happens to be a kernel thread, regardless of which task
the signal is aimed at. The same call with the same target succeeds or
fails depending only on what the CPU was running:
bpf_send_signal_task() from tp_btf/workqueue_execute_start : -EPERM
bpf_send_signal_task() from tp_btf/sys_enter : 0
The check was carried over from bpf_probe_write_user() when
bpf_send_signal() was added in commit 8b401f9ed244 ("bpf: implement
bpf_send_signal() helper"). There it guards a user memory write, but
bpf_send_signal_common() does no user memory access, so the check has
nothing to guard here. It is also already a no-op outside x86.
Remove it, and drop the part of the comment above it that described
the memory access checks, as none remain.
Fixes: 6280cf718db0 ("bpf: Implement bpf_send_signal_task() kfunc")
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Aditya Sharma <adi.sharma@zohomail.in>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20260819124324.43162-1-adi.sharma@zohomail.in/T/#u
Link: https://patch.msgid.link/20261001072449.1377267-2-adi.sharma@zohomail.in
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/bpf_trace.c | 9 |
1 files changed, 3 insertions, 6 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index dfac5e1b8f40..14adfb85fdb2 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -867,15 +867,12 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type, struct task_struc siginfo = &info; } - /* Similar to bpf_probe_write_user, task needs to be - * in a sound condition and kernel memory access be - * permitted in order to send signal to the current - * task. + /* + * Similar to bpf_probe_write_user, task needs to be + * in a sound condition. */ if (unlikely(task->flags & (PF_KTHREAD | PF_EXITING))) return -EPERM; - if (unlikely(!nmi_uaccess_okay())) - return -EPERM; /* Task should not be pid=1 to avoid kernel panic. */ if (unlikely(is_global_init(task))) return -EPERM; |