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 --- lib/vsprintf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'lib') diff --git a/lib/vsprintf.c b/lib/vsprintf.c index f0c35d9b65bf..cc281f5895f9 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2186,7 +2186,7 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode, bool no_hash_pointers __ro_after_init; EXPORT_SYMBOL_GPL(no_hash_pointers); -static int __init no_hash_pointers_enable(char *str) +int __init no_hash_pointers_enable(char *str) { if (no_hash_pointers) return 0; -- cgit v1.2.3