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Thadeu Lima de Souza Cascardo 5779e2f0cc efi/x86: use naked RET on mixed mode call wrapper 
commit 51a6fa0732 upstream.

When running with return thunks enabled under 32-bit EFI, the system
crashes with:

  kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
  BUG: unable to handle page fault for address: 000000005bc02900
  #PF: supervisor instruction fetch in kernel mode
  #PF: error_code(0x0011) - permissions violation
  PGD 18f7063 P4D 18f7063 PUD 18ff063 PMD 190e063 PTE 800000005bc02063
  Oops: 0011 [#1] PREEMPT SMP PTI
  CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.19.0-rc6+ #166
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
  RIP: 0010:0x5bc02900
  Code: Unable to access opcode bytes at RIP 0x5bc028d6.
  RSP: 0018:ffffffffb3203e10 EFLAGS: 00010046
  RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000048
  RDX: 000000000190dfac RSI: 0000000000001710 RDI: 000000007eae823b
  RBP: ffffffffb3203e70 R08: 0000000001970000 R09: ffffffffb3203e28
  R10: 747563657865206c R11: 6c6977203a696665 R12: 0000000000001710
  R13: 0000000000000030 R14: 0000000001970000 R15: 0000000000000001
  FS:  0000000000000000(0000) GS:ffff8e013ca00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0018 ES: 0018 CR0: 0000000080050033
  CR2: 000000005bc02900 CR3: 0000000001930000 CR4: 00000000000006f0
  Call Trace:
   ? efi_set_virtual_address_map+0x9c/0x175
   efi_enter_virtual_mode+0x4a6/0x53e
   start_kernel+0x67c/0x71e
   x86_64_start_reservations+0x24/0x2a
   x86_64_start_kernel+0xe9/0xf4
   secondary_startup_64_no_verify+0xe5/0xeb

That's because it cannot jump to the return thunk from the 32-bit code.

Using a naked RET and marking it as safe allows the system to proceed
booting.

Fixes: aa3d480315 ("x86: Use return-thunk in asm code")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: <stable@vger.kernel.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-07-25 11:26:53 +02:00
arch efi/x86: use naked RET on mixed mode call wrapper 2022-07-25 11:26:53 +02:00
block block: Fix handling of offline queues in blk_mq_alloc_request_hctx() 2022-06-22 14:13:17 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:13:17 +02:00
crypto crypto: memneq - move into lib/ 2022-06-22 14:13:18 +02:00
Documentation x86/bugs: Add retbleed=ibpb 2022-07-25 11:26:44 +02:00
drivers intel_idle: Disable IBRS during long idle 2022-07-25 11:26:43 +02:00
fs ext4: fix race condition between ext4_write and ext4_convert_inline_data 2022-07-21 21:20:02 +02:00
include objtool: Re-add UNWIND_HINT_{SAVE_RESTORE} 2022-07-25 11:26:47 +02:00
init Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug 2022-06-09 10:21:25 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-09 10:21:17 +02:00
kernel signal handling: don't use BUG_ON() for debugging 2022-07-21 21:20:18 +02:00
lib ida: don't use BUG_ON() for debugging 2022-07-12 16:32:23 +02:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm: split huge PUD on wp_huge_pud fallback 2022-07-21 21:19:59 +02:00
net net: tipc: fix possible refcount leak in tipc_sk_create() 2022-07-21 21:20:14 +02:00
samples x86: Prepare inline-asm for straight-line-speculation 2022-07-25 11:26:29 +02:00
scripts x86/retbleed: Add fine grained Kconfig knobs 2022-07-25 11:26:50 +02:00
security x86/retbleed: Add fine grained Kconfig knobs 2022-07-25 11:26:50 +02:00
sound ASoC: madera: Fix event generation for rate controls 2022-07-21 21:20:16 +02:00
tools tools/insn: Restore the relative include paths for cross building 2022-07-25 11:26:52 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:25:48 +01:00
virt KVM: Prevent module exit until all VMs are freed 2022-04-08 14:40:38 +02:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.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 kbuild: generate Module.symvers only when vmlinux exists 2021-05-19 10:12:59 +02:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
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 MAINTAINERS: add Amir as xfs maintainer for 5.10.y 2022-07-02 16:39:22 +02:00
Makefile x86/retbleed: Add fine grained Kconfig knobs 2022-07-25 11:26:50 +02:00
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.