rseq: Remove broken uapi field layout on 32-bit little endian

The rseq rseq_cs.ptr.{ptr32,padding} uapi endianness handling is entirely wrong on 32-bit little endian: a preprocessor logic mistake wrongly uses the big endian field layout on 32-bit little endian architectures. Fortunately, those ptr32 accessors were never used within the kernel, and only meant as a convenience for user-space. Remove those and replace the whole rseq_cs union by a __u64 type, as this is the only thing really needed to express the ABI. Document how 32-bit architectures are meant to interact with this field.

Mathieu Desnoyers committed 4 years ago

Commit bfdf4e61 parent 5c105d52 files · +8 −20Browse files

Showing the changes to kernel (1 of 2 files). Show all

Unified · Split

kernel/rseq.c+4−4

@@ -128,10 +128,10 @@ static int rseq_get_rseq_cs(struct task_struct t, struct rseq_cs rseq_cs) · 127 unmodified lines
128	128	int ret;
129	129
130	130	#ifdef CONFIG_64BIT
131		− if (get_user(ptr, &t->rseq->rseq_cs.ptr64))
	131	+ if (get_user(ptr, &t->rseq->rseq_cs))
132	132	return -EFAULT;
133	133	#else
134		− if (copy_from_user(&ptr, &t->rseq->rseq_cs.ptr64, sizeof(ptr)))
	134	+ if (copy_from_user(&ptr, &t->rseq->rseq_cs, sizeof(ptr)))
135	135	return -EFAULT;
136	136	#endif
137	137	if (!ptr) {
@@ -217,9 +217,9 @@ static int clear_rseq_cs(struct task_struct *t) · 79 unmodified lines
217	217	* Set rseq_cs to NULL.
218	218	*/
219	219	#ifdef CONFIG_64BIT
220		− return put_user(0UL, &t->rseq->rseq_cs.ptr64);
	220	+ return put_user(0UL, &t->rseq->rseq_cs);
221	221	#else
222		− if (clear_user(&t->rseq->rseq_cs.ptr64, sizeof(t->rseq->rseq_cs.ptr64)))
	222	+ if (clear_user(&t->rseq->rseq_cs, sizeof(t->rseq->rseq_cs)))
223	223	return -EFAULT;
224	224	return 0;
225	225	#endif