To avoid false positives, assume that reading from the task stack always produces initialized values. Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> --- Link: https://linux-review.googlesource.com/id/I9e2350bf3e88688dd83537e12a23456480141997 --- arch/x86/include/asm/unwind.h | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h index 7cede4dc21f00..87acc90875b74 100644 --- a/arch/x86/include/asm/unwind.h +++ b/arch/x86/include/asm/unwind.h @@ -128,18 +128,19 @@ unsigned long unwind_recover_ret_addr(struct unwind_state *state, } /* - * This disables KASAN checking when reading a value from another task's stack, - * since the other task could be running on another CPU and could have poisoned - * the stack in the meantime. + * This disables KASAN/KMSAN checking when reading a value from another task's + * stack, since the other task could be running on another CPU and could have + * poisoned the stack in the meantime. Frame pointers are uninitialized by + * default, so for KMSAN we mark the return value initialized unconditionally. */ -#define READ_ONCE_TASK_STACK(task, x) \ -({ \ - unsigned long val; \ - if (task == current) \ - val = READ_ONCE(x); \ - else \ - val = READ_ONCE_NOCHECK(x); \ - val; \ +#define READ_ONCE_TASK_STACK(task, x) \ +({ \ + unsigned long val; \ + if (task == current && !IS_ENABLED(CONFIG_KMSAN)) \ + val = READ_ONCE(x); \ + else \ + val = READ_ONCE_NOCHECK(x); \ + val; \ }) static inline bool task_on_another_cpu(struct task_struct *task) -- 2.36.0.rc2.479.g8af0fa9b8e-goog
