bpf: check that BPF programs run with preemption disabled

Introduce cant_sleep() macro for annotation of functions that
cannot sleep.

Use it in BPF_PROG_RUN to catch execution of BPF programs in
preemptable context.

Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 28 insertions, 0 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d8d76a65cfdd..7cbb5658be80 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6162,6 +6162,34 @@ void ___might_sleep(const char *file, int line, int preempt_offset)
         add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
 }
 EXPORT_SYMBOL(___might_sleep);
+
+void __cant_sleep(const char *file, int line, int preempt_offset)
+{
+        static unsigned long prev_jiffy;
+
+        if (irqs_disabled())
+                return;
+
+        if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
+                return;
+
+        if (preempt_count() > preempt_offset)
+                return;
+
+        if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
+                return;
+        prev_jiffy = jiffies;
+
+        printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);
+        printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
+                        in_atomic(), irqs_disabled(),
+                        current->pid, current->comm);
+
+        debug_show_held_locks(current);
+        dump_stack();
+        add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
+}
+EXPORT_SYMBOL_GPL(__cant_sleep);
 #endif
 
 #ifdef CONFIG_MAGIC_SYSRQ