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: Tue, 11 Feb 2025 11:07:50 -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
print_address_description() is run with a raw_spinlock_t acquired and
interrupt disabled. find_vm_area() 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. 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/20250211160750.1301353-1-longman@xxxxxxxxxx
Fixes: c056a364e954 ("kasan: print virtual mapping info in reports")
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@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>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kasan/report.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
--- a/mm/kasan/report.c~kasan-dont-call-find_vm_area-in-rt-kernel
+++ a/mm/kasan/report.c
@@ -398,9 +398,20 @@ static void print_address_description(vo
pr_err("\n");
}
- if (is_vmalloc_addr(addr)) {
- struct vm_struct *va = find_vm_area(addr);
+ if (!is_vmalloc_addr(addr))
+ goto print_page;
+ /*
+ * 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.
+ */
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
+ static DEFINE_WAIT_OVERRIDE_MAP(vmalloc_map, LD_WAIT_SLEEP);
+ 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"
@@ -410,8 +421,13 @@ static void print_address_description(vo
page = vmalloc_to_page(addr);
}
+ lock_map_release(&vmalloc_map);
+ } else {
+ pr_err("The buggy address %px belongs to a vmalloc virtual mapping\n",
+ addr);
}
+print_page:
if (page) {
pr_err("The buggy address belongs to the physical page:\n");
dump_page(page, "kasan: bad access detected");
_
Patches currently in -mm which might be from longman@xxxxxxxxxx are
kasan-dont-call-find_vm_area-in-rt-kernel.patch
