github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-06-08 14:42:37 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph
Linux kernel source tree
797,632 Commits 1 Branch 934 Tags 20 GiB
C 97%
Assembly 1%
Shell 0.6%
Rust 0.5%
Python 0.4%
Other 0.3%
9b7dbeedf8
Go to file
Arvind Sankar 9b7dbeedf8 x86/boot: Correct relocation destination on old linkers 
[ Upstream commit 5214028dd8 ]

For the 32-bit kernel, as described in

  6d92bc9d48 ("x86/build: Build compressed x86 kernels as PIE"),

pre-2.26 binutils generates R_386_32 relocations in PIE mode. Since the
startup code does not perform relocation, any reloc entry with R_386_32
will remain as 0 in the executing code.

Commit

  974f221c84 ("x86/boot: Move compressed kernel to the end of the
                 decompression buffer")

added a new symbol _end but did not mark it hidden, which doesn't give
the correct offset on older linkers. This causes the compressed kernel
to be copied beyond the end of the decompression buffer, rather than
flush against it. This region of memory may be reserved or already
allocated for other purposes by the bootloader.

Mark _end as hidden to fix. This changes the relocation from R_386_32 to
R_386_RELATIVE even on the pre-2.26 binutils.

For 64-bit, this is not strictly necessary, as the 64-bit kernel is only
built as PIE if the linker supports -z noreloc-overflow, which implies
binutils-2.27+, but for consistency, mark _end as hidden here too.

The below illustrates the before/after impact of the patch using
binutils-2.25 and gcc-4.6.4 (locally compiled from source) and QEMU.

  Disassembly before patch:
    48:   8b 86 60 02 00 00       mov    0x260(%esi),%eax
    4e:   2d 00 00 00 00          sub    $0x0,%eax
                          4f: R_386_32    _end
  Disassembly after patch:
    48:   8b 86 60 02 00 00       mov    0x260(%esi),%eax
    4e:   2d 00 f0 76 00          sub    $0x76f000,%eax
                          4f: R_386_RELATIVE      *ABS*

Dump from extract_kernel before patch:
	early console in extract_kernel
	input_data: 0x0207c098 <--- this is at output + init_size
	input_len: 0x0074fef1
	output: 0x01000000
	output_len: 0x00fa63d0
	kernel_total_size: 0x0107c000
	needed_size: 0x0107c000

Dump from extract_kernel after patch:
	early console in extract_kernel
	input_data: 0x0190d098 <--- this is at output + init_size - _end
	input_len: 0x0074fef1
	output: 0x01000000
	output_len: 0x00fa63d0
	kernel_total_size: 0x0107c000
	needed_size: 0x0107c000

Fixes: 974f221c84 ("x86/boot: Move compressed kernel to the end of the decompression buffer")
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200207214926.3564079-1-nivedita@alum.mit.edu
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-06-22 09:05:18 +02:00
arch x86/boot: Correct relocation destination on old linkers 2020-06-22 09:05:18 +02:00
block block, bfq: fix use-after-free in bfq_idle_slice_timer_body 2020-04-17 10:48:42 +02:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto gcc-10: avoid shadowing standard library 'free()' in crypto 2020-05-20 08:18:46 +02:00
Documentation dt-bindings: display: mediatek: control dpi pins mode to avoid leakage 2020-06-22 09:05:13 +02:00
drivers mwifiex: Fix memory corruption in dump_station 2020-06-22 09:05:17 +02:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs xfs: fix duplicate verification from xfs_qm_dqflush() 2020-06-22 09:05:16 +02:00
include kgdb: Fix spurious true from in_dbg_master() 2020-06-22 09:05:15 +02:00
init x86: Fix early boot crash on gcc-10, third try 2020-05-20 08:18:49 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:18:40 +02:00
kernel sched/core: Fix illegal RCU from offline CPUs 2020-06-22 09:05:14 +02:00
lib lib/mpi: Fix 64-bit MIPS build with Clang 2020-06-22 09:05:14 +02:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm/slub: fix a memory leak in sysfs_slab_add() 2020-06-22 09:05:08 +02:00
net netfilter: nft_nat: return EOPNOTSUPP if type or flags are not supported 2020-06-22 09:05:14 +02:00
samples samples: bpf: Fix build error 2020-06-03 08:19:31 +02:00
scripts gcc-common.h: Update for GCC 10 2020-05-27 17:37:30 +02:00
security Smack: slab-out-of-bounds in vsscanf 2020-06-22 09:05:08 +02:00
sound ALSA: pcm: disallow linking stream to itself 2020-06-22 09:05:03 +02:00
tools selftests/bpf: Fix memory leak in extract_build_id() 2020-06-22 09:05:14 +02:00
usr initramfs: restore default compression behavior 2020-04-13 10:44:59 +02:00
virt KVM: arm64: Synchronize sysreg state on injecting an AArch32 exception 2020-06-22 09:05:09 +02:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 16:38:49 +01:00
Makefile Linux 4.19.128 2020-06-10 21:35:02 +02:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

README 

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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.