linux-kernel - [PATCH AUTOSEL 6.6 12/15] objtool, panic: Disable SMAP in __stack_chk

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Message-Id: <20250407181417.3183475-12-sashal@kernel.org>
Date: Mon,  7 Apr 2025 14:14:12 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Josh Poimboeuf <jpoimboe@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Kees Cook <keescook@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Sasha Levin <sashal@...nel.org>,
	peterz@...radead.org,
	pmladek@...e.com,
	jani.nikula@...el.com,
	john.ogness@...utronix.de,
	gregkh@...uxfoundation.org,
	joel.granados@...nel.org,
	jfalempe@...hat.com,
	takakura@...inux.co.jp
Subject: [PATCH AUTOSEL 6.6 12/15] objtool, panic: Disable SMAP in __stack_chk_fail()

From: Josh Poimboeuf <jpoimboe@...nel.org>

[ Upstream commit 72c774aa9d1e16bfd247096935e7dae194d84929 ]

__stack_chk_fail() can be called from uaccess-enabled code.  Make sure
uaccess gets disabled before calling panic().

Fixes the following warning:

  kernel/trace/trace_branch.o: error: objtool: ftrace_likely_update+0x1ea: call to __stack_chk_fail() with UACCESS enabled

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Kees Cook <keescook@...omium.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Link: https://lore.kernel.org/r/a3e97e0119e1b04c725a8aa05f7bc83d98e657eb.1742852847.git.jpoimboe@kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/panic.c        | 6 ++++++
 tools/objtool/check.c | 5 ++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/kernel/panic.c b/kernel/panic.c
index ef9f9a4e928de..d7973e9754748 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -763,9 +763,15 @@ device_initcall(register_warn_debugfs);
  */
 __visible noinstr void __stack_chk_fail(void)
 {
+	unsigned long flags;
+
 	instrumentation_begin();
+	flags = user_access_save();
+
 	panic("stack-protector: Kernel stack is corrupted in: %pB",
 		__builtin_return_address(0));
+
+	user_access_restore(flags);
 	instrumentation_end();
 }
 EXPORT_SYMBOL(__stack_chk_fail);
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 665dccdd6b0af..46638e5a8576a 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1225,12 +1225,15 @@ static const char *uaccess_safe_builtin[] = {
 	"__ubsan_handle_load_invalid_value",
 	/* STACKLEAK */
 	"stackleak_track_stack",
+	/* TRACE_BRANCH_PROFILING */
+	"ftrace_likely_update",
+	/* STACKPROTECTOR */
+	"__stack_chk_fail",
 	/* misc */
 	"csum_partial_copy_generic",
 	"copy_mc_fragile",
 	"copy_mc_fragile_handle_tail",
 	"copy_mc_enhanced_fast_string",
-	"ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
 	"rep_stos_alternative",
 	"rep_movs_alternative",
 	"__copy_user_nocache",
-- 
2.39.5