Re: [PATCH 5.15.y] scripts/sorttable: fix orc_sort_cmp() to maintain symmetry and transitivity

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

Found matching upstream commit: 0210d251162f4033350a94a43f95b1c39ec84a90


Status in newer kernel trees:
6.12.y | Not found
6.6.y | Not found
6.1.y | Not found
5.15.y | Not found

Note: The patch differs from the upstream commit:
---
1:  0210d251162f ! 1:  02225d4eea29 scripts/sorttable: fix orc_sort_cmp() to maintain symmetry and transitivity
    @@ Commit message
     
         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_TYPE_UNDEFINED, it could result in both a < b
    +    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].
    @@ Commit message
         Transitivity: If x < y and y < z, then x < z.
     
         Fix the comparison logic to return 0 when both entries are
    -    ORC_TYPE_UNDEFINED, ensuring compliance with qsort() requirements.
    +    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
    @@ Commit message
         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>
     
      ## scripts/sorttable.h ##
     @@ scripts/sorttable.h: static inline unsigned long orc_ip(const int *ip)
    @@ scripts/sorttable.h: static int orc_sort_cmp(const void *_a, const void *_b)
      	 */
      	orc_a = g_orc_table + (a - g_orc_ip_table);
     +	orc_b = g_orc_table + (b - g_orc_ip_table);
    -+	if (orc_a->type == ORC_TYPE_UNDEFINED && orc_b->type == ORC_TYPE_UNDEFINED)
    ++	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->type == ORC_TYPE_UNDEFINED ? -1 : 1;
    + 	return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
      }
      
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y       |  Success    |  Success   |