From 8bb43a99bef50e507733a67f40e8e6fdedd88170 Mon Sep 17 00:00:00 2001
From: Kuan-Wei Chiu <visitorckw@gmail.com>
Date: Tue, 7 Jan 2025 01:44:59 +0800
Subject: [PATCH] scripts/sorttable: fix orc_sort_cmp() to maintain symmetry
and transitivity
The orc_sort_cmp() function, used with qsort(), previously violated the
symmetry and transitivity rules required by the C standard. Specifically,
when both entries are ORC_REG_UNDEFINED, it could result in both a < b
and b < a, which breaks the required symmetry and transitivity. This can
lead to undefined behavior and incorrect sorting results, potentially
causing memory corruption in glibc implementations [1].
Symmetry: If x < y, then y > x.
Transitivity: If x < y and y < z, then x < z.
Fix the comparison logic to return 0 when both entries are
ORC_REG_UNDEFINED, ensuring compliance with qsort() requirements.
Link: https://www.qualys.com/2024/01/30/qsort.txt [1]
Link: https://lkml.kernel.org/r/20241226140332.2670689-1-visitorckw@gmail.com
Fixes: 57fa18994285 ("scripts/sorttable: Implement build-time ORC unwind table sorting")
Fixes: fb799447ae29 ("x86,objtool: Split UNWIND_HINT_EMPTY in two")
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Cc: Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw>
Cc: <chuang@cs.nycu.edu.tw>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shile Zhang <shile.zhang@linux.alibaba.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 0210d251162f4033350a94a43f95b1c39ec84a90)
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
scripts/sorttable.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/scripts/sorttable.h b/scripts/sorttable.h
index deb7c1d3e979d..f0ba2bf5a8864 100644
--- a/scripts/sorttable.h
+++ b/scripts/sorttable.h
@@ -110,7 +110,7 @@ static inline unsigned long orc_ip(const int *ip)
static int orc_sort_cmp(const void *_a, const void *_b)
{
- struct orc_entry *orc_a;
+ struct orc_entry *orc_a, *orc_b;
const int *a = g_orc_ip_table + *(int *)_a;
const int *b = g_orc_ip_table + *(int *)_b;
unsigned long a_val = orc_ip(a);
@@ -128,6 +128,10 @@ static int orc_sort_cmp(const void *_a, const void *_b)
* whitelisted .o files which didn't get objtool generation.
*/
orc_a = g_orc_table + (a - g_orc_ip_table);
+ orc_b = g_orc_table + (b - g_orc_ip_table);
+ if (orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end &&
+ orc_b->sp_reg == ORC_REG_UNDEFINED && !orc_b->end)
+ return 0;
return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
}
--
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