Commit dc3b8ae9 authored May 25, 2018 by Arnd Bergmann Committed by Daniel Borkmann May 28, 2018

bpf: avoid -Wmaybe-uninitialized warning



The stack_map_get_build_id_offset() function is too long for gcc to track
whether 'work' may or may not be initialized at the end of it, leading
to a false-positive warning:

kernel/bpf/stackmap.c: In function 'stack_map_get_build_id_offset':
kernel/bpf/stackmap.c:334:13: error: 'work' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This removes the 'in_nmi_ctx' flag and uses the state of that variable
itself to see if it got initialized.

Fixes: bae77c5e ("bpf: enable stackmap with build_id in nmi context")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent 53c8036c

kernel/bpf/stackmap.c

+3 −4

Original line number	Diff line number	Diff line
		@@ -285,11 +285,10 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
		{
		int i;
		struct vm_area_struct *vma;
		bool in_nmi_ctx = in_nmi();
		bool irq_work_busy = false;
		struct stack_map_irq_work *work;
		struct stack_map_irq_work *work = NULL;

		if (in_nmi_ctx) {
		if (in_nmi()) {
		work = this_cpu_ptr(&up_read_work);
		if (work->irq_work.flags & IRQ_WORK_BUSY)
		/* cannot queue more up_read, fallback */
		@@ -328,7 +327,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
		id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
		}

		if (!in_nmi_ctx) {
		if (!work) {
		up_read(&current->mm->mmap_sem);
		} else {
		work->sem = &current->mm->mmap_sem;