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malloc: Do not use MAP_NORESERVE to allocate heap segments (RHEL-21884) 

Resolves: RHEL-21884
This commit is contained in:
Arjun Shankar 2024-03-12 17:10:19 +01:00
parent b11febd624
commit 5a35e9b70f
2 changed files with 78 additions and 1 deletions
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73
glibc-RHEL-21884.patch Normal file
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@ -0,0 +1,73 @@
commit 85860ad6eaf4c9739318f6b2a1ff7c2fa6b12ab5
Author: Florian Weimer <fweimer@redhat.com>
Date: Mon Aug 15 16:45:40 2022 +0200
malloc: Do not use MAP_NORESERVE to allocate heap segments
Address space for heap segments is reserved in a mmap call with
MAP_ANONYMOUS | MAP_PRIVATE and protection flags PROT_NONE. This
reservation does not count against the RSS limit of the process or
system. Backing memory is allocated using mprotect in alloc_new_heap
and grow_heap, and at this point, the allocator expects the kernel
to provide memory (subject to memory overcommit).
The SIGSEGV that might generate due to MAP_NORESERVE (according to
the mmap manual page) does not seem to occur in practice, it's always
SIGKILL from the OOM killer. Even if there is a way that SIGSEGV
could be generated, it is confusing to applications that this only
happens for secondary heaps, not for large mmap-based allocations,
and not for the main arena.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Conflicts:
malloc/arena.c
(huge page support was added upstream)
diff --git a/malloc/arena.c b/malloc/arena.c
index 667484630ed0afa5..2852783355d3d869 100644
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -466,8 +466,7 @@ new_heap (size_t size, size_t top_pad)
p2 = MAP_FAILED;
if (aligned_heap_area)
{
- p2 = (char *) MMAP (aligned_heap_area, HEAP_MAX_SIZE, PROT_NONE,
- MAP_NORESERVE);
+ p2 = (char *) MMAP (aligned_heap_area, HEAP_MAX_SIZE, PROT_NONE, 0);
aligned_heap_area = NULL;
if (p2 != MAP_FAILED && ((unsigned long) p2 & (HEAP_MAX_SIZE - 1)))
{
@@ -477,7 +476,7 @@ new_heap (size_t size, size_t top_pad)
}
if (p2 == MAP_FAILED)
{
- p1 = (char *) MMAP (0, HEAP_MAX_SIZE << 1, PROT_NONE, MAP_NORESERVE);
+ p1 = (char *) MMAP (0, HEAP_MAX_SIZE << 1, PROT_NONE, 0);
if (p1 != MAP_FAILED)
{
p2 = (char *) (((unsigned long) p1 + (HEAP_MAX_SIZE - 1))
@@ -493,7 +492,7 @@ new_heap (size_t size, size_t top_pad)
{
/* Try to take the chance that an allocation of only HEAP_MAX_SIZE
is already aligned. */
- p2 = (char *) MMAP (0, HEAP_MAX_SIZE, PROT_NONE, MAP_NORESERVE);
+ p2 = (char *) MMAP (0, HEAP_MAX_SIZE, PROT_NONE, 0);
if (p2 == MAP_FAILED)
return 0;
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 375f50f5db13e234..fe80b8239756a7c9 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -1112,10 +1112,6 @@ static mchunkptr mremap_chunk(mchunkptr p, size_t new_size);
# define MAP_ANONYMOUS MAP_ANON
#endif
-#ifndef MAP_NORESERVE
-# define MAP_NORESERVE 0
-#endif
-
#define MMAP(addr, size, prot, flags) \
__mmap((addr), (size), (prot), (flags)|MAP_ANONYMOUS|MAP_PRIVATE, -1, 0)

6
glibc.spec
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@ -155,7 +155,7 @@ end \
Summary: The GNU libc libraries
Name: glibc
Version: %{glibcversion}
Release: 102%{?dist}
Release: 103%{?dist}
# In general, GPLv2+ is used by programs, LGPLv2+ is used for
# libraries.
@ -811,6 +811,7 @@ Patch574: glibc-RHEL-21556.patch
Patch575: glibc-RHEL-23472.patch
Patch576: glibc-RHEL-20172-1.patch
Patch577: glibc-RHEL-20172-2.patch
Patch578: glibc-RHEL-21884.patch
##############################################################################
# Continued list of core "glibc" package information:
@ -2969,6 +2970,9 @@ update_gconv_modules_cache ()
%endif
%changelog
* Tue Mar 12 2024 Arjun Shankar <arjun@redhat.com> - 2.34-103
- malloc: Do not use MAP_NORESERVE to allocate heap segments (RHEL-21884)
* Fri Mar 8 2024 DJ Delorie <dj@redhat.com> - 2.34-102
- Add glibc.cpu.prefer_map_32bit_exec tunable (RHEL-20172)