The quilt patch titled Subject: scs: fix a wrong parameter in __scs_magic has been removed from the -mm tree. Its filename was scs-fix-a-wrong-parameter-in-__scs_magic.patch
This patch was dropped because it was merged into the mm-nonmm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------ From: Zhichi Lin zhichi.lin@vivo.com Subject: scs: fix a wrong parameter in __scs_magic Date: Sat, 11 Oct 2025 16:22:22 +0800
__scs_magic() needs a 'void *' variable, but a 'struct task_struct *' is given. 'task_scs(tsk)' is the starting address of the task's shadow call stack, and '__scs_magic(task_scs(tsk))' is the end address of the task's shadow call stack. Here should be '__scs_magic(task_scs(tsk))'.
The user-visible effect of this bug is that when CONFIG_DEBUG_STACK_USAGE is enabled, the shadow call stack usage checking function (scs_check_usage) would scan an incorrect memory range. This could lead to:
1. **Inaccurate stack usage reporting**: The function would calculate wrong usage statistics for the shadow call stack, potentially showing incorrect value in kmsg.
2. **Potential kernel crash**: If the value of __scs_magic(tsk)is greater than that of __scs_magic(task_scs(tsk)), the for loop may access unmapped memory, potentially causing a kernel panic. However, this scenario is unlikely because task_struct is allocated via the slab allocator (which typically returns lower addresses), while the shadow call stack returned by task_scs(tsk) is allocated via vmalloc(which typically returns higher addresses).
However, since this is purely a debugging feature (CONFIG_DEBUG_STACK_USAGE), normal production systems should be not unaffected. The bug only impacts developers and testers who are actively debugging stack usage with this configuration enabled.
Link: https://lkml.kernel.org/r/20251011082222.12965-1-zhichi.lin@vivo.com Fixes: 5bbaf9d1fcb9 ("scs: Add support for stack usage debugging") Signed-off-by: Jiyuan Xie xiejiyuan@vivo.com Signed-off-by: Zhichi Lin zhichi.lin@vivo.com Reviewed-by: Sami Tolvanen samitolvanen@google.com Acked-by: Will Deacon will@kernel.org Cc: Andrey Konovalov andreyknvl@gmail.com Cc: Kees Cook keescook@chromium.org Cc: Marco Elver elver@google.com Cc: Will Deacon will@kernel.org Cc: Yee Lee yee.lee@mediatek.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
kernel/scs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/scs.c~scs-fix-a-wrong-parameter-in-__scs_magic +++ a/kernel/scs.c @@ -135,7 +135,7 @@ static void scs_check_usage(struct task_ if (!IS_ENABLED(CONFIG_DEBUG_STACK_USAGE)) return;
- for (p = task_scs(tsk); p < __scs_magic(tsk); ++p) { + for (p = task_scs(tsk); p < __scs_magic(task_scs(tsk)); ++p) { if (!READ_ONCE_NOCHECK(*p)) break; used += sizeof(*p); _
Patches currently in -mm which might be from zhichi.lin@vivo.com are