[tip: objtool/urgent] objtool, panic: Disable SMAP in __stack_chk_fail()

[tip-bot2 for Josh Poimboeuf]

The following commit has been merged into the objtool/urgent branch of tip:

Commit-ID:     c2299757eb5bbc121177a23559eff8f66e944381
Gitweb:        https://git.kernel.org/tip/c2299757eb5bbc121177a23559eff8f66e944381
Author:        Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate:    Mon, 24 Mar 2025 14:56:07 -07:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 25 Mar 2025 09:20:28 +01:00

objtool, panic: Disable SMAP in __stack_chk_fail()

__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@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/a3e97e0119e1b04c725a8aa05f7bc83d98e657eb.1742852847.git.jpoimboe@xxxxxxxxxx
---
 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 d8635d5..f9f0c51 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -832,9 +832,15 @@ 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 0caabf0..3bf2992 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1194,12 +1194,15 @@ 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",