[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-ID: <20230815230809.GA973560@hirez.programming.kicks-ass.net>
Date: Wed, 16 Aug 2023 01:08:09 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: jpoimboe@...nel.org, x86@...nel.org
Cc: baron@...mai.com, rostedt@...dmis.org, ardb@...nel.org,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
linux-kernel@...r.kernel.org, christian@...cart.de,
song@...nel.org, mcgrof@...nel.org
Subject: [PATCH] x86/static_call: Fix __static_call_fixup()
Christian reported spurious module 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 dies.
And while the module rework made this slightly more likely to happen,
it's always been possible.
Fixes: ee88d363d156 ("x86,static_call: Use alternative RET encoding")
Reported-by: Christian Bricart <christian@...cart.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
arch/x86/kernel/static_call.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c
index b70670a98597..2e67512d7104 100644
--- a/arch/x86/kernel/static_call.c
+++ b/arch/x86/kernel/static_call.c
@@ -186,6 +186,16 @@ EXPORT_SYMBOL_GPL(arch_static_call_transform);
*/
bool __static_call_fixup(void *tramp, u8 op, void *dest)
{
+ /*
+ * Not all .return_sites are a static_call trampoline (most are not).
+ * Check if the next 3 bytes 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 (!kernel_text_address(tramp+7))
+ return false;
+
if (memcmp(tramp+5, tramp_ud, 3)) {
/* Not a trampoline site, not our problem. */
return false;
Powered by blists - more mailing lists