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Sven Schnelle 86f48f922b s390/mmap: disable mmap alignment when randomize_va_space = 0
Stefan reported a test case fail in libc. The test runs with
randomize_va_space set to zero, i.e. disabled randomization. Additionally,
it runs the program with the dynamic loader. Looking at the failure showed
that the heap was placed right before some pages mapped from the binary.
This made memory allocation fail after a few allocations.

Normally, when address randomization is switched off and the binary is
loaded from the dynamic loader, the kernel places the binary below the
128MB top gap. So the address map would look like this:

3fff7fd1000-3fff7fd2000 r--p 00000000 5e:01 1447115 /lib/ld64.so.1
3fff7fd2000-3fff7ff2000 r-xp 00001000 5e:01 1447115 /lib/ld64.so.1
3fff7ff2000-3fff7ffc000 r--p 00021000 5e:01 1447115 /lib/ld64.so.1
3fff7ffc000-3fff7ffe000 r--p 0002a000 5e:01 1447115 /lib/ld64.so.1
3fff7ffe000-3fff8000000 rw-p 0002c000 5e:01 1447115 /lib/ld64.so.1
3fff8000000-3fff8021000 rw-p 00000000 00:00 0       [heap]
3fffffda000-3ffffffb000 rw-p 00000000 00:00 0       [stack]
3ffffffc000-3ffffffe000 r--p 00000000 00:00 0       [vvar]
3ffffffe000-40000000000 r-xp 00000000 00:00 0       [vdso]

However, commit 1f6b83e5e4 ("s390: avoid z13 cache aliasing") introduced
a mmap alignment mask of 8MB. With this commit, the memory map now
looks like this:

3fff7f80000-3fff7f81000 r--p 00000000 5e:01 1447115 /lib/ld64.so.1
3fff7f81000-3fff7fa1000 r-xp 00001000 5e:01 1447115 /lib/ld64.so.1
3fff7fa1000-3fff7fab000 r--p 00021000 5e:01 1447115 /lib/ld64.so.1
3fff7fab000-3fff7fad000 r--p 0002a000 5e:01 1447115 /lib/ld64.so.1
3fff7fad000-3fff7faf000 rw-p 0002c000 5e:01 1447115 /lib/ld64.so.1
3fff7faf000-3fff7fd0000 rw-p 00000000 00:00 0       [heap]
3fff7fdc000-3fff8000000 rw-p 00000000 00:00 0
3fffffda000-3ffffffb000 rw-p 00000000 00:00 0       [stack]
3ffffffc000-3ffffffe000 r--p 00000000 00:00 0       [vvar]
3ffffffe000-40000000000 r-xp 00000000 00:00 0       [vdso]

The reason for this placement is that the elf loader loads the binary to
end at mmap_base (0x3fff8000000 on s390). This would result in a start
address of 0x3fff7fd1000, but due to the alignment requirement of 8MB,
mmap chooses 0x3fff7f80000. This causes a gap between the end of the
mapped binary and mmap_base. When the next non-shared and non-file pages
are mapped, mmap searches from top to bottom and the first free space it
finds is the gap which is now present. This leaves only a few pages for
the heap. With enabled address space randomization this doesn't happen
because the binary is mapped to a completely different memory area.

Fix this by disabling the mmap alignment when address space randomization
is disabled. This is in line with what other architectures are doing.

Reported-by: Stefan Liebler <stli@linux.ibm.com>
Tested-by: Stefan Liebler <stli@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
2024-02-09 13:58:14 +01:00
arch s390/mmap: disable mmap alignment when randomize_va_space = 0 2024-02-09 13:58:14 +01:00
block block: Fix where bio IO priority gets set 2024-02-01 11:00:06 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto crypto: scomp - fix req->dst buffer overflow 2023-12-29 11:25:56 +08:00
Documentation USB driver fixes for 6.8-rc3 2024-02-04 06:52:29 +00:00
drivers s390/vmur: fix virtual vs physical address confusion 2024-02-09 13:58:14 +01:00
fs Miscellaneous bug fixes and cleanups in ext4's multi-block allocator 2024-02-04 07:33:01 +00:00
include Miscellaneous bug fixes and cleanups in ext4's multi-block allocator 2024-02-04 07:33:01 +00:00
init Kconfig: Disable -Wstringop-overflow for GCC globally 2024-02-01 14:57:17 -08:00
io_uring io_uring/net: fix sr->len for IORING_OP_RECV with MSG_WAITALL and buffers 2024-02-01 06:42:36 -07:00
ipc shm: Slim down dependencies 2023-12-20 19:26:31 -05:00
kernel Tracing and eventfs fixes for v6.8: 2024-02-02 15:32:58 -08:00
lib linux_kselftest-kunit-fixes-6.8-rc3 2024-01-30 15:12:58 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm 22 hotfixes. 11 are cc:stable and the remainder address post-6.7 issues 2024-01-29 17:12:16 -08:00
net Including fixes from netfilter. 2024-02-01 12:39:54 -08:00
rust Rust changes for v6.8 2024-01-11 13:05:41 -08:00
samples samples/cgroup: add .gitignore file for generated samples 2024-01-24 11:52:40 -08:00
scripts Kbuild fixes for v6.8 2024-02-01 11:57:42 -08:00
security lsm/stable-6.8 PR 20240131 2024-02-01 10:00:28 -08:00
sound ASoC: Fixes for v6.8 2024-02-01 19:40:42 +01:00
tools perf tools fixes for v6.8: 2024-02-03 12:52:36 +00:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt Generic: 2024-01-17 13:03:37 -08:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.mailmap Char/Misc and other Driver changes for 6.8-rc1 2024-01-17 16:47:17 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: supplement of zswap maintainers update 2024-01-25 23:52:21 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS update to point people to the new tree for i2c host driver 2024-02-04 06:47:45 +00:00
Makefile Linux 6.8-rc3 2024-02-04 12:20:36 +00:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.