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Subject[PATCH, net-next 2/2] bpf: avoid -Wmaybe-uninitialized warning
Date
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: bae77c5eb5b2 ("bpf: enable stackmap with build_id in nmi context")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
kernel/bpf/stackmap.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index b59ace0f0f09..b675a3f3d141 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -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;
--
2.9.0
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