The patch titled
elf: reduce default MAX_MAP_COUNT to be safe value
has been added to the -mm tree. Its filename is
elf-reduce-default-max_map_count-to-be-safe-value.patch
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------------------------------------------------------
Subject: elf: reduce default MAX_MAP_COUNT to be safe value
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
With ELF, at generating coredump, some more headers other than used vmas
are added. When, maxp_map_count == 65536, a core generated by following
kinds of code can be unreadable because the number of ELF's program header
is written in 16bit in Ehdr (please see elf.h) and the number overflows.
==
... = mmap(); (munmap, mprotect, etc...)
if (failed)
abort();
==
This can be happen in mmap/munmap/mprotect/etc...which calls split_vma().
I think 65536 is not safe as _default_ because core-dump can be corrupted
when we need to look into coredump. This reduce it to 65500 for avoiding
unexpected corrupted core. (I confirmed 65530 can work well with my tiny
program.)
Anyway, max_map_count can be enlarged by sysctl if a user is brave..
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Jakub Jelinek <jakub@xxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Cc: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN include/linux/sched.h~elf-reduce-default-max_map_count-to-be-safe-value include/linux/sched.h
--- a/include/linux/sched.h~elf-reduce-default-max_map_count-to-be-safe-value
+++ a/include/linux/sched.h
@@ -351,7 +351,7 @@ struct nsproxy;
struct user_namespace;
/* Maximum number of active map areas.. This is a random (large) number */
-#define DEFAULT_MAX_MAP_COUNT 65536
+#define DEFAULT_MAX_MAP_COUNT 65500
extern int sysctl_max_map_count;
_
Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are
origin.patch
migration-only-migrate_prep-once-per-move_pages.patch
page-allocator-use-integer-fields-lookup-for-gfp_zone-and-check-for-errors-in-flags-passed-to-the-page-allocator.patch
page-allocator-use-integer-fields-lookup-for-gfp_zone-and-check-for-errors-in-flags-passed-to-the-page-allocator-fix-gfp-zone-patch.patch
mm-add-swap-cache-interface-for-swap-reference.patch
mm-modify-swap_map-and-add-swap_has_cache-flag.patch
mm-modify-swap_map-and-add-swap_has_cache-flag-update.patch
mm-reuse-unused-swap-entry-if-necessary.patch
mm-reuse-unused-swap-entry-if-necessary-update.patch
vmscan-handle-may_swap-more-strictly.patch
cgroups-forbid-noprefix-if-mounting-more-than-just-cpuset-subsystem.patch
cgroups-forbid-noprefix-if-mounting-more-than-just-cpuset-subsystem-fix.patch
cgroups-forbid-noprefix-if-mounting-more-than-just-cpuset-subsystem-fix2.patch
memcg-add-file-based-rss-accounting.patch
memcg-add-file-based-rss-accounting-fix-mem_cgroup_update_mapped_file_stat-oops.patch
memcg-remove-mem_cgroup_cache_charge_swapin.patch
memcg-remove-some-redundant-checks.patch
memcg-remove-unneeded-forward-declaration-from-schedh.patch
memcg-fix-swap-accounting.patch
memcg-fix-swap-accounting-update.patch
memcg-fix-behavior-under-memorylimit-equals-to-memswlimit.patch
memcg-add-interface-to-reset-limits.patch
elf-reduce-default-max_map_count-to-be-safe-value.patch
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