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@xxxxxxxxx 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@xxxxxxxxx> Cc: Ching-Chun (Jim) Huang <jserv@xxxxxxxxxxxxxxxx> Cc: <chuang@xxxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Shile Zhang <shile.zhang@xxxxxxxxxxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> (cherry picked from commit 0210d251162f4033350a94a43f95b1c39ec84a90) Signed-off-by: Kuan-Wei Chiu <visitorckw@xxxxxxxxx> --- scripts/sorttable.h | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/scripts/sorttable.h b/scripts/sorttable.h index a2baa2fefb13..fb385d0f3cc2 100644 --- a/scripts/sorttable.h +++ b/scripts/sorttable.h @@ -103,7 +103,7 @@ 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); @@ -120,8 +120,12 @@ static int orc_sort_cmp(const void *_a, const void *_b) * These terminator entries exist to handle any gaps created by * whitelisted .o files which didn't get objtool generation. */ - orc_a = g_orc_table + (a - g_orc_ip_table); - return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1; + 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; } static void *sort_orctable(void *arg) -- 2.34.1
