X-Git-Url: https://git.kernelconcepts.de/?a=blobdiff_plain;f=mm%2Fmaccess.c;h=d159b1c96e484d902f6edb34ebb5a83a3977bd57;hb=2d4de05aac6be83cf69b7ec29244d10ec1dd8701;hp=34fe24759ed1f32cb58cd38d2245ae7b82dc7f37;hpb=ed14ee0eea8b6808025356cecc87a8007885263f;p=karo-tx-linux.git

diff --git a/mm/maccess.c b/mm/maccess.c
index 34fe24759ed1..d159b1c96e48 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -13,6 +13,11 @@
  *
  * Safely read from address @src to the buffer at @dst.  If a kernel fault
  * happens, handle that and return -EFAULT.
+ *
+ * We ensure that the copy_from_user is executed in atomic context so that
+ * do_page_fault() doesn't attempt to take mmap_sem.  This makes
+ * probe_kernel_read() suitable for use within regions where the caller
+ * already holds mmap_sem, or other locks which nest inside mmap_sem.
  */
 
 long __weak probe_kernel_read(void *dst, const void *src, size_t size)
@@ -99,5 +104,5 @@ long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
 	pagefault_enable();
 	set_fs(old_fs);
 
-	return ret < 0 ? ret : src - unsafe_addr;
+	return ret ? -EFAULT : src - unsafe_addr;
 }