kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-10-14 05:55:17 +00:00
Code Issues Releases Packages Activity
No description
1,141,312 commits 116 branches 5,791 tags 5.6 GiB
  • C 96.9%
  • Assembly 0.9%
  • Rust 0.6%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
Michael Ellerman 18bac7de24 powerpc/64s/radix: Fix crash with unaligned relocated kernel 
commit 98d0219e04 upstream.

If a relocatable kernel is loaded at an address that is not 2MB aligned
and told not to relocate to zero, the kernel can crash due to
mark_rodata_ro() incorrectly changing some read-write data to read-only.

Scenarios where the misalignment can occur are when the kernel is
loaded by kdump or using the RELOCATABLE_TEST config option.

Example crash with the kernel loaded at 5MB:

  Run /sbin/init as init process
  BUG: Unable to handle kernel data access on write at 0xc000000000452000
  Faulting instruction address: 0xc0000000005b6730
  Oops: Kernel access of bad area, sig: 11 [#1]
  LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
  CPU: 1 PID: 1 Comm: init Not tainted 6.2.0-rc1-00011-g349188be4841 #166
  Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202 0xf000005 of:SLOF,git-5b4c5a hv:linux,kvm pSeries
  NIP:  c0000000005b6730 LR: c000000000ae9ab8 CTR: 0000000000000380
  REGS: c000000004503250 TRAP: 0300   Not tainted  (6.2.0-rc1-00011-g349188be4841)
  MSR:  8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 44288480  XER: 00000000
  CFAR: c0000000005b66ec DAR: c000000000452000 DSISR: 0a000000 IRQMASK: 0
  ...
  NIP memset+0x68/0x104
  LR  zero_user_segments.constprop.0+0xa8/0xf0
  Call Trace:
    ext4_mpage_readpages+0x7f8/0x830
    ext4_readahead+0x48/0x60
    read_pages+0xb8/0x380
    page_cache_ra_unbounded+0x19c/0x250
    filemap_fault+0x58c/0xae0
    __do_fault+0x60/0x100
    __handle_mm_fault+0x1230/0x1a40
    handle_mm_fault+0x120/0x300
    ___do_page_fault+0x20c/0xa80
    do_page_fault+0x30/0xc0
    data_access_common_virt+0x210/0x220

This happens because mark_rodata_ro() tries to change permissions on the
range _stext..__end_rodata, but _stext sits in the middle of the 2MB
page from 4MB to 6MB:

  radix-mmu: Mapped 0x0000000000000000-0x0000000000200000 with 2.00 MiB pages (exec)
  radix-mmu: Mapped 0x0000000000200000-0x0000000000400000 with 2.00 MiB pages
  radix-mmu: Mapped 0x0000000000400000-0x0000000002400000 with 2.00 MiB pages (exec)

The logic that changes the permissions assumes the linear mapping was
split correctly at boot, so it marks the entire 2MB page read-only. That
leads to the write fault above.

To fix it, the boot time mapping logic needs to consider that if the
kernel is running at a non-zero address then _stext is a boundary where
it must split the mapping.

That leads to the mapping being split correctly, allowing the rodata
permission change to take happen correctly, with no spillover:

  radix-mmu: Mapped 0x0000000000000000-0x0000000000200000 with 2.00 MiB pages (exec)
  radix-mmu: Mapped 0x0000000000200000-0x0000000000400000 with 2.00 MiB pages
  radix-mmu: Mapped 0x0000000000400000-0x0000000000500000 with 64.0 KiB pages
  radix-mmu: Mapped 0x0000000000500000-0x0000000000600000 with 64.0 KiB pages (exec)
  radix-mmu: Mapped 0x0000000000600000-0x0000000002400000 with 2.00 MiB pages (exec)

If the kernel is loaded at a 2MB aligned address, the mapping continues
to use 2MB pages as before:

  radix-mmu: Mapped 0x0000000000000000-0x0000000000200000 with 2.00 MiB pages (exec)
  radix-mmu: Mapped 0x0000000000200000-0x0000000000400000 with 2.00 MiB pages
  radix-mmu: Mapped 0x0000000000400000-0x0000000002c00000 with 2.00 MiB pages (exec)
  radix-mmu: Mapped 0x0000000002c00000-0x0000000100000000 with 2.00 MiB pages

Fixes: c55d7b5e64 ("powerpc: Remove STRICT_KERNEL_RWX incompatibility with RELOCATABLE")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230110124753.1325426-1-mpe@ellerman.id.au
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-02-09 11:28:26 +01:00
arch powerpc/64s/radix: Fix crash with unaligned relocated kernel 2023-02-09 11:28:26 +01:00
block block, bfq: fix uaf for bfqq in bic_set_bfqq() 2023-02-09 11:28:06 +01:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto use less confusing names for iov_iter direction initializers 2023-02-09 11:28:04 +01:00
Documentation dt-bindings: i2c: renesas,rzv2m: Fix SoC specific string 2023-02-01 08:34:51 +01:00
drivers iio:adc:twl6030: Enable measurement of VAC 2023-02-09 11:28:26 +01:00
fs Squashfs: fix handling and sanity checking of xattr_ids count 2023-02-09 11:28:23 +01:00
include nvmem: core: remove nvmem_config wp_gpio 2023-02-09 11:28:24 +01:00
init gcc: disable -Warray-bounds for gcc-11 too 2023-01-14 10:33:43 +01:00
io_uring use less confusing names for iov_iter direction initializers 2023-02-09 11:28:04 +01:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel kernel/irq/irqdomain.c: fix memory leak with using debugfs_lookup() 2023-02-09 11:28:21 +01:00
lib maple_tree: fix mas_empty_area_rev() lower bound validation 2023-02-09 11:28:23 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm migrate: hugetlb: check for hugetlb shared PMD in node migration 2023-02-09 11:28:23 +01:00
net can: isotp: handle wait_event_interruptible() return values 2023-02-09 11:28:15 +01:00
rust rust: print: avoid evaluating arguments in pr_* macros in unsafe blocks 2023-02-06 08:06:34 +01:00
samples ftrace: Export ftrace_free_filter() to modules 2023-02-01 08:34:37 +01:00
scripts kbuild: modinst: Fix build error when CONFIG_MODULE_SIG_KEY is a PKCS#11 URI 2023-02-09 11:28:11 +01:00
security use less confusing names for iov_iter direction initializers 2023-02-09 11:28:04 +01:00
sound ASoC: SOF: sof-audio: prepare_widgets: Check swidget for NULL on sink failure 2023-02-09 11:28:26 +01:00
tools cgroup/cpuset: Fix wrong check in update_parent_subparts_cpumask() 2023-02-09 11:28:15 +01:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt kvm/vfio: Fix potential deadlock on vfio group_lock 2023-02-01 08:34:36 +01:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -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: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
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 panic: Expose "warn_count" to sysfs 2023-01-24 07:24:41 +01:00
Makefile Linux 6.1.10 2023-02-06 08:06:34 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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.

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.