mirrors/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2025-11-04 02:30:34 +02:00
Code Issues Projects Releases Packages Wiki Activity Actions

x86/static_call: Fix __static_call_fixup()

Browse source 
Christian reported spurious module load crashes after some of Song's
module memory layout patches.

Turns out that if the very last instruction on the very last page of the
module is a 'JMP __x86_return_thunk' then __static_call_fixup() will
trip a fault and die.

And while the module rework made this slightly more likely to happen,
it's always been possible.

Fixes: ee88d363d1 ("x86,static_call: Use alternative RET encoding")
Reported-by: Christian Bricart <christian@bricart.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lkml.kernel.org/r/20230816104419.GA982867@hirez.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra 2023-08-16 12:44:19 +02:00
parent dbf4600877
commit 5409730962
1 changed files with 13 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

13
arch/x86/kernel/static_call.c
View file

@ -186,6 +186,19 @@ EXPORT_SYMBOL_GPL(arch_static_call_transform);
*/ */
bool __static_call_fixup(void *tramp, u8 op, void *dest) bool __static_call_fixup(void *tramp, u8 op, void *dest)
{ {
unsigned long addr = (unsigned long)tramp;
/*
* Not all .return_sites are a static_call trampoline (most are not).
* Check if the 3 bytes after the return are still kernel text, if not,
* then this definitely is not a trampoline and we need not worry
* further.
*
* This avoids the memcmp() below tripping over pagefaults etc..
*/
if (((addr >> PAGE_SHIFT) != ((addr + 7) >> PAGE_SHIFT)) &&
!kernel_text_address(addr + 7))
return false;
if (memcmp(tramp+5, tramp_ud, 3)) { if (memcmp(tramp+5, tramp_ud, 3)) {
/* Not a trampoline site, not our problem. */ /* Not a trampoline site, not our problem. */
return false; return false;