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Christophe Leroy acca57217c powerpc/signal32: Fix Oops on sigreturn with unmapped VDSO 
PPC32 encounters a KUAP fault when trying to handle a signal with
VDSO unmapped.

	Kernel attempted to read user page (7fc07ec0) - exploit attempt? (uid: 0)
	BUG: Unable to handle kernel data access on read at 0x7fc07ec0
	Faulting instruction address: 0xc00111d4
	Oops: Kernel access of bad area, sig: 11 [#1]
	BE PAGE_SIZE=16K PREEMPT CMPC885
	CPU: 0 PID: 353 Comm: sigreturn_vdso Not tainted 5.12.0-rc4-s3k-dev-01553-gb30c310ea220 #4814
	NIP:  c00111d4 LR: c0005a28 CTR: 00000000
	REGS: cadb3dd0 TRAP: 0300   Not tainted  (5.12.0-rc4-s3k-dev-01553-gb30c310ea220)
	MSR:  00009032 <EE,ME,IR,DR,RI>  CR: 48000884  XER: 20000000
	DAR: 7fc07ec0 DSISR: 88000000
	GPR00: c0007788 cadb3e90 c28d4a40 7fc07ec0 7fc07ed0 000004e0 7fc07ce0 00000000
	GPR08: 00000001 00000001 7fc07ec0 00000000 28000282 1001b828 100a0920 00000000
	GPR16: 100cac0c 100b0000 105c43a4 105c5685 100d0000 100d0000 100d0000 100b2e9e
	GPR24: ffffffff 105c43c8 00000000 7fc07ec8 cadb3f40 cadb3ec8 c28d4a40 00000000
	NIP [c00111d4] flush_icache_range+0x90/0xb4
	LR [c0005a28] handle_signal32+0x1bc/0x1c4
	Call Trace:
	[cadb3e90] [100d0000] 0x100d0000 (unreliable)
	[cadb3ec0] [c0007788] do_notify_resume+0x260/0x314
	[cadb3f20] [c000c764] syscall_exit_prepare+0x120/0x184
	[cadb3f30] [c00100b4] ret_from_syscall+0xc/0x28
	--- interrupt: c00 at 0xfe807f8
	NIP:  0fe807f8 LR: 10001060 CTR: c0139378
	REGS: cadb3f40 TRAP: 0c00   Not tainted  (5.12.0-rc4-s3k-dev-01553-gb30c310ea220)
	MSR:  0000d032 <EE,PR,ME,IR,DR,RI>  CR: 28000482  XER: 20000000

	GPR00: 00000025 7fc081c0 77bb1690 00000000 0000000a 28000482 00000001 0ff03a38
	GPR08: 0000d032 00006de5 c28d4a40 00000009 88000482 1001b828 100a0920 00000000
	GPR16: 100cac0c 100b0000 105c43a4 105c5685 100d0000 100d0000 100d0000 100b2e9e
	GPR24: ffffffff 105c43c8 00000000 77ba7628 10002398 10010000 10002124 00024000
	NIP [0fe807f8] 0xfe807f8
	LR [10001060] 0x10001060
	--- interrupt: c00
	Instruction dump:
	38630010 7c001fac 38630010 4200fff0 7c0004ac 4c00012c 4e800020 7c001fac
	2c0a0000 38630010 4082ffcc 4bffffe4 <7c00186c> 2c070000 39430010 4082ff8c
	---[ end trace 3973fb72b049cb06 ]---

This is because flush_icache_range() is called on user addresses.

The same problem was detected some time ago on PPC64. It was fixed by
enabling KUAP in commit 59bee45b97 ("powerpc/mm: Fix missing KUAP
disable in flush_coherent_icache()").

PPC32 doesn't use flush_coherent_icache() and fallbacks on
clean_dcache_range() and invalidate_icache_range().

We could fix it similarly by enabling user access in those functions,
but this is overkill for just flushing two instructions.

The two instructions are 8 bytes aligned, so a single dcbst/icbi is
enough to flush them. Do like __patch_instruction() and inline
a dcbst followed by an icbi just after the write of the instructions,
while user access is still allowed. The isync is not required because
rfi will be used to return to user.

icbi() is handled as a read so read-write user access is needed.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/bde9154e5351a5ac7bca3d59cdb5a5e8edacbb79.1617199569.git.christophe.leroy@csgroup.eu
 		2021-04-02 00:16:23 +11:00
Documentation block-5.12-2021-03-05 2021-03-05 12:59:37 -08:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
arch powerpc/signal32: Fix Oops on sigreturn with unmapped VDSO 2021-04-02 00:16:23 +11:00
block block/bfq: update comments and default value in docs for fifo_expire 2021-03-02 11:25:38 -07:00
certs certs: Replace K{U,G}IDT_INIT() with GLOBAL_ROOT_{U,G}ID 2021-01-21 16:16:10 +00:00
crypto Keyrings miscellany 2021-02-23 16:09:23 -08:00
drivers PCI: rpadlpar: Fix potential drc_name corruption in store functions 2021-03-17 13:48:07 +11:00
fs pstore fixes for v5.12-rc2 2021-03-05 17:21:25 -08:00
include block-5.12-2021-03-05 2021-03-05 12:59:37 -08:00
init kbuild: fix UNUSED_KSYMS_WHITELIST for Clang LTO 2021-02-28 15:19:21 +09:00
ipc fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
kernel io_uring-5.12-2021-03-05 2021-03-05 12:44:43 -08:00
lib Merge branch 'kmap-conversion-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux 2021-03-01 11:24:18 -08:00
mm swap: fix swapfile read/write offset 2021-03-02 17:25:46 -07:00
net io_uring-worker.v3-2021-02-25 2021-02-27 08:29:02 -08:00
samples treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
scripts gcc-plugins fixes for v5.12-rc2 2021-03-05 17:23:03 -08:00
security Keyrings miscellany 2021-02-23 16:09:23 -08:00
sound ALSA: hda/realtek: Apply dual codec quirks for MSI Godlike X570 board 2021-03-03 15:25:03 +01:00
tools * Doc fixes 2021-03-04 11:26:17 -08:00
usr Kbuild updates for v5.12 2021-02-25 10:17:31 -08:00
virt KVM: x86/mmu: Consider the hva in mmu_notifier retry 2021-02-22 13:16:53 -05:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore clang-lto series for v5.12-rc1 2021-02-23 09:28:51 -08:00
.mailmap treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS RISC-V Patches for the 5.12 Merge Window 2021-02-26 10:28:35 -08:00
Makefile Linux 5.12-rc2 2021-03-05 17:33:41 -08:00
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.