[PATCH] mm: relax ptrace mode in process_vm_readv(2)

[Alexey Dobriyan <adobriyan@gmail.com>]

It is more natural to check for read-from-memory permissions in case of
process_vm_readv() as PTRACE_MODE_ATTACH is equivalent to write
permissions.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 mm/process_vm_access.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -204,7 +204,7 @@ static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
 		goto free_proc_pages;
 	}
 
-	mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS);
+	mm = mm_access(task, vm_write ? PTRACE_MODE_ATTACH_REALCREDS : PTRACE_MODE_READ_REALCREDS);
 	if (!mm || IS_ERR(mm)) {
 		rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
 		/*