mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GC…

…C versions Randy reported objtool triggered on his (GCC-7.4) build: lib/strncpy_from_user.o: warning: objtool: strncpy_from_user()+0x315: call to __ubsan_handle_add_overflow() with UACCESS enabled lib/strnlen_user.o: warning: objtool: strnlen_user()+0x337: call to __ubsan_handle_sub_overflow() with UACCESS enabled This is due to UBSAN generating signed-overflow-UB warnings where it should not. Prior to GCC-8 UBSAN ignored -fwrapv (which the kernel uses through -fno-strict-overflow). Make the functions use 'unsigned long' throughout. Reported-by: Randy Dunlap <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Acked-by: Randy Dunlap <[email protected]> # build-tested Acked-by: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]>
ambv · Apr 24, 2019 · 29da93f · 29da93f
1 parent 6ae8656
commit 29da93f
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Showing 2 changed files with 5 additions and 4 deletions.
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
@@ -23,10 +23,11 @@
  * hit it), 'max' is the address space maximum (and we return
  * -EFAULT if we hit it).
  */
-static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max)
+static inline long do_strncpy_from_user(char *dst, const char __user *src,
+					unsigned long count, unsigned long max)
 {
 	const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
-	long res = 0;
+	unsigned long res = 0;
 
 	/*
 	 * Truncate 'max' to the user-specified limit, so that

diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
@@ -28,7 +28,7 @@
 static inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max)
 {
 	const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
-	long align, res = 0;
+	unsigned long align, res = 0;
 	unsigned long c;
 
 	/*
@@ -42,7 +42,7 @@ static inline long do_strnlen_user(const char __user *src, unsigned long count,
 	 * Do everything aligned. But that means that we
 	 * need to also expand the maximum..
 	 */
-	align = (sizeof(long) - 1) & (unsigned long)src;
+	align = (sizeof(unsigned long) - 1) & (unsigned long)src;
 	src -= align;
 	max += align;