From 792702911f581f7793962fbeb99d5c3a1b28f4c3 Mon Sep 17 00:00:00 2001 From: Stephen Boyd Date: Mon, 28 Jun 2021 19:34:52 -0700 Subject: slub: force on no_hash_pointers when slub_debug is enabled Obscuring the pointers that slub shows when debugging makes for some confusing slub debug messages: Padding overwritten. 0x0000000079f0674a-0x000000000d4dce17 Those addresses are hashed for kernel security reasons. If we're trying to be secure with slub_debug on the commandline we have some big problems given that we dump whole chunks of kernel memory to the kernel logs. Let's force on the no_hash_pointers commandline flag when slub_debug is on the commandline. This makes slub debug messages more meaningful and if by chance a kernel address is in some slub debug object dump we will have a better chance of figuring out what went wrong. Note that we don't use %px in the slub code because we want to reduce the number of places that %px is used in the kernel. This also nicely prints a big fat warning at kernel boot if slub_debug is on the commandline so that we know that this kernel shouldn't be used on production systems. [akpm@linux-foundation.org: fix build with CONFIG_SLUB_DEBUG=n] Link: https://lkml.kernel.org/r/20210601182202.3011020-5-swboyd@chromium.org Signed-off-by: Stephen Boyd Acked-by: Vlastimil Babka Acked-by: Petr Mladek Cc: Joe Perches Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Muchun Song Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 15d8bad3d2f2..bf950621febf 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -357,6 +357,8 @@ int sscanf(const char *, const char *, ...); extern __scanf(2, 0) int vsscanf(const char *, const char *, va_list); +extern int no_hash_pointers_enable(char *str); + extern int get_option(char **str, int *pint); extern char *get_options(const char *str, int nints, int *ints); extern unsigned long long memparse(const char *ptr, char **retptr); -- cgit v1.2.3-59-g8ed1b