The patch titled
Subject: kmemleak: drop (age <increasing>) from leak record
has been added to the -mm mm-unstable branch. Its filename is
kmemleak-drop-age-increasing-from-leak-record.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kmemleak-drop-age-increasing-from-leak-record.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Jim Cromie <jim.cromie@xxxxxxxxx>
Subject: kmemleak: drop (age <increasing>) from leak record
Date: Thu, 16 Nov 2023 15:43:17 -0700
Patch series "tweak kmemleak report format".
These 2 patches make minor changes to the report:
1st strips "age <increasing>" from output. This makes the output
idempotent; unchanging until a new leak is reported.
2nd adds the backtrace.checksum to the "backtrace:" line. This lets a
user see repeats without actually reading the whole backtrace. So now
the backtrace line looks like this:
backtrace (crc 603070071):
I surveyed for un-wanted effects upon users:
Syzkaller parses kmemleak in executor/common_linux.h:
static void check_leaks(char** frames, int nframes)
It just counts occurrences of "unreferenced object", specifically it
does not look for "age", nor would it choke on "crc" being added.
github has 3 repos with "kmemleak" mentioned, all are moribund.
gitlab has 0 hits on "kmemleak".
This patch (of 2):
Displaying age is pretty, but counter-productive; it changes with
current-time, so it surrenders idempotency of the output, which breaks
simple hash-based cataloging of the records by the user.
The trouble: sequential reads, wo new leaks, get new results:
:#> sum /sys/kernel/debug/kmemleak
53439 74 /sys/kernel/debug/kmemleak
:#> sum /sys/kernel/debug/kmemleak
59066 74 /sys/kernel/debug/kmemleak
and age is why (nothing else changes):
:#> grep -v age /sys/kernel/debug/kmemleak | sum
58894 67
:#> grep -v age /sys/kernel/debug/kmemleak | sum
58894 67
Since jiffies is already printed in the "comm" line, age adds nothing.
Notably, syzkaller reads kmemleak only for "unreferenced object", and
won't care about this reform of age-ism. A few moribund github repos
mention it, but don't compile.
Link: https://lkml.kernel.org/r/20231116224318.124209-1-jim.cromie@xxxxxxxxx
Link: https://lkml.kernel.org/r/20231116224318.124209-2-jim.cromie@xxxxxxxxx
Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kmemleak.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
--- a/mm/kmemleak.c~kmemleak-drop-age-increasing-from-leak-record
+++ a/mm/kmemleak.c
@@ -355,14 +355,12 @@ static void print_unreferenced(struct se
int i;
unsigned long *entries;
unsigned int nr_entries;
- unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);
nr_entries = stack_depot_fetch(object->trace_handle, &entries);
warn_or_seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
object->pointer, object->size);
- warn_or_seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
- object->comm, object->pid, object->jiffies,
- msecs_age / 1000, msecs_age % 1000);
+ warn_or_seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu\n",
+ object->comm, object->pid, object->jiffies);
hex_dump_object(seq, object);
warn_or_seq_printf(seq, " backtrace:\n");
_
Patches currently in -mm which might be from jim.cromie@xxxxxxxxx are
kmemleak-drop-age-increasing-from-leak-record.patch
kmemleak-add-checksum-to-backtrace-report.patch
