git/linux-net
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/ synced 2026-04-18 06:33:43 -04:00
Code Issues Packages Projects Releases Wiki Activity

x86/bug: Fix BUG_FORMAT vs KASLR

Browse Source 
Encoding a relative NULL pointer doesn't work for KASLR, when the
whole kernel image gets shifted, the __bug_table and the target string
get shifted by the same amount and the relative offset is preserved.

However when the target is an absolute 0 value and the __bug_table
gets moved about, the end result in a pointer equivalent to
kaslr_offset(), not NULL.

Notably, this will generate SHN_UNDEF relocations, and Ard would
really like to not have those at all.

Use the empty string to denote no-string.

Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
This commit is contained in:
Peter Zijlstra
2025-11-26 10:55:17 +01:00
parent 860238af7a
commit d62e4f2b95
2 changed files with 17 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
lib/bug.c
View File

@@ -144,7 +144,17 @@ static const char *bug_get_format(struct bug_entry *bug)
const char *format = NULL;
#ifdef HAVE_ARCH_BUG_FORMAT
#ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
format = (const char *)&bug->format_disp + bug->format_disp;
/*
* Allow an architecture to:
* - relative encode NULL (difficult vs KASLR);
* - use a literal 0 (there are no valid objects inside
* the __bug_table itself to refer to after all);
* - use an empty string.
*/
if (bug->format_disp)
format = (const char *)&bug->format_disp + bug->format_disp;
if (format && format[0] == '\0')
format = NULL;
#else
format = bug->format;
#endif