The change is very straightforward, and helps unify the syscall
interface for struct-from-userspace syscalls.
Signed-off-by: Aleksa Sarai <cyphar@xxxxxxxxxx>
---
kernel/events/core.c | 47 +++++++++-----------------------------------
1 file changed, 9 insertions(+), 38 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0463c1151bae..038ed126bc1b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10498,55 +10498,26 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
u32 size;
int ret;
- if (!access_ok(uattr, PERF_ATTR_SIZE_VER0))
- return -EFAULT;
-
- /*
- * zero the full structure, so that a short copy will be nice.
- */
+ /* Zero the full structure, so that a short copy will be nice. */
memset(attr, 0, sizeof(*attr));
ret = get_user(size, &uattr->size);
if (ret)
return ret;
- if (size > PAGE_SIZE) /* silly large */
- goto err_size;
-
- if (!size) /* abi compat */
+ /* ABI compatibility quirk: */
+ if (!size)
size = PERF_ATTR_SIZE_VER0;
-
- if (size < PERF_ATTR_SIZE_VER0)
+ if (size < PERF_ATTR_SIZE_VER0 || size > PAGE_SIZE)
goto err_size;
- /*
- * If we're handed a bigger struct than we know of,
- * ensure all the unknown bits are 0 - i.e. new
- * user-space does not rely on any kernel feature
- * extensions we dont know about yet.
- */
- if (size > sizeof(*attr)) {
- unsigned char __user *addr;
- unsigned char __user *end;
- unsigned char val;
-
- addr = (void __user *)uattr + sizeof(*attr);
- end = (void __user *)uattr + size;
-
- for (; addr < end; addr++) {
- ret = get_user(val, addr);
- if (ret)
- return ret;
- if (val)
- goto err_size;
- }
- size = sizeof(*attr);
+ ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size);
+ if (ret) {
+ if (ret == -E2BIG)
+ goto err_size;
+ return ret;
}
- ret = copy_from_user(attr, uattr, size);
- if (ret)
- return -EFAULT;
-
attr->size = size;
if (attr->__reserved_1)
--
2.23.0
