The patch titled
Subject: kasan: don't call find_vm_area() in RT kernel
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
kasan-dont-call-find_vm_area-in-rt-kernel.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-dont-call-find_vm_area-in-rt-kernel.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Waiman Long <longman@xxxxxxxxxx>
Subject: kasan: don't call find_vm_area() in RT kernel
Date: Wed, 12 Feb 2025 11:21:51 -0500
The following bug report appeared with a test run in a RT debug kernel.
[ 3359.353842] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
[ 3359.353848] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 140605, name: kunit_try_catch
[ 3359.353853] preempt_count: 1, expected: 0
:
[ 3359.353933] Call trace:
:
[ 3359.353955] rt_spin_lock+0x70/0x140
[ 3359.353959] find_vmap_area+0x84/0x168
[ 3359.353963] find_vm_area+0x1c/0x50
[ 3359.353966] print_address_description.constprop.0+0x2a0/0x320
[ 3359.353972] print_report+0x108/0x1f8
[ 3359.353976] kasan_report+0x90/0xc8
[ 3359.353980] __asan_load1+0x60/0x70
Commit e30a0361b851 ("kasan: make report_lock a raw spinlock") changes
report_lock to a raw_spinlock_t to avoid a similar RT problem. The
print_address_description() function is called with report_lock acquired
and interrupt disabled. However, the find_vm_area() function still needs
to acquire a spinlock_t which becomes a sleeping lock in the RT kernel.
IOW, we can't call find_vm_area() in a RT kernel and changing report_lock
to a raw_spinlock_t is not enough to completely solve this RT kernel
problem.
Fix this bug report by skipping the find_vm_area() call in this case and
just print out the address as is.
For !RT kernel, follow the example set in commit 0cce06ba859a
("debugobjects,locking: Annotate debug_object_fill_pool() wait type
violation") and use DEFINE_WAIT_OVERRIDE_MAP() to avoid a spinlock_t
inside raw_spinlock_t warning.
Link: https://lkml.kernel.org/r/20250212162151.1599059-1-longman@xxxxxxxxxx
Fixes: e30a0361b851 ("kasan: make report_lock a raw spinlock")
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Acked-by: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Dmitriy Vyukov <dvyukov@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Mariano Pache <npache@xxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kasan/report.c | 47 +++++++++++++++++++++++++++++++-------------
1 file changed, 34 insertions(+), 13 deletions(-)
--- a/mm/kasan/report.c~kasan-dont-call-find_vm_area-in-rt-kernel
+++ a/mm/kasan/report.c
@@ -370,6 +370,38 @@ static inline bool init_task_stack_addr(
sizeof(init_thread_union.stack));
}
+/*
+ * RT kernel cannot call find_vm_area() in atomic context. For !RT kernel,
+ * prevent spinlock_t inside raw_spinlock_t warning by raising wait-type
+ * to WAIT_SLEEP.
+ *
+ * Return: page pointer or NULL
+ */
+static inline struct page *kasan_print_vmalloc_info_ret_page(void *addr)
+{
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
+ static DEFINE_WAIT_OVERRIDE_MAP(vmalloc_map, LD_WAIT_SLEEP);
+ struct page *page = NULL;
+ struct vm_struct *va;
+
+ lock_map_acquire_try(&vmalloc_map);
+ va = find_vm_area(addr);
+ if (va) {
+ pr_err("The buggy address belongs to the virtual mapping at\n"
+ " [%px, %px) created by:\n"
+ " %pS\n",
+ va->addr, va->addr + va->size, va->caller);
+ pr_err("\n");
+
+ page = vmalloc_to_page(addr);
+ }
+ lock_map_release(&vmalloc_map);
+ return page;
+ }
+ pr_err("The buggy address %px belongs to a vmalloc virtual mapping\n", addr);
+ return NULL;
+}
+
static void print_address_description(void *addr, u8 tag,
struct kasan_report_info *info)
{
@@ -398,19 +430,8 @@ static void print_address_description(vo
pr_err("\n");
}
- if (is_vmalloc_addr(addr)) {
- struct vm_struct *va = find_vm_area(addr);
-
- if (va) {
- pr_err("The buggy address belongs to the virtual mapping at\n"
- " [%px, %px) created by:\n"
- " %pS\n",
- va->addr, va->addr + va->size, va->caller);
- pr_err("\n");
-
- page = vmalloc_to_page(addr);
- }
- }
+ if (is_vmalloc_addr(addr))
+ page = kasan_print_vmalloc_info_ret_page(addr);
if (page) {
pr_err("The buggy address belongs to the physical page:\n");
_
Patches currently in -mm which might be from longman@xxxxxxxxxx are
kasan-dont-call-find_vm_area-in-rt-kernel.patch
