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Haorong Lu 79fc40a29d riscv: signal: handle syscall restart before get_signal 
commit ce4f78f1b5 upstream.

In the current riscv implementation, blocking syscalls like read() may
not correctly restart after being interrupted by ptrace. This problem
arises when the syscall restart process in arch_do_signal_or_restart()
is bypassed due to changes to the regs->cause register, such as an
ebreak instruction.

Steps to reproduce:
1. Interrupt the tracee process with PTRACE_SEIZE & PTRACE_INTERRUPT.
2. Backup original registers and instruction at new_pc.
3. Change pc to new_pc, and inject an instruction (like ebreak) to this
   address.
4. Resume with PTRACE_CONT and wait for the process to stop again after
   executing ebreak.
5. Restore original registers and instructions, and detach from the
   tracee process.
6. Now the read() syscall in tracee will return -1 with errno set to
   ERESTARTSYS.

Specifically, during an interrupt, the regs->cause changes from
EXC_SYSCALL to EXC_BREAKPOINT due to the injected ebreak, which is
inaccessible via ptrace so we cannot restore it. This alteration breaks
the syscall restart condition and ends the read() syscall with an
ERESTARTSYS error. According to include/linux/errno.h, it should never
be seen by user programs. X86 can avoid this issue as it checks the
syscall condition using a register (orig_ax) exposed to user space.
Arm64 handles syscall restart before calling get_signal, where it could
be paused and inspected by ptrace/debugger.

This patch adjusts the riscv implementation to arm64 style, which also
checks syscall using a kernel register (syscallno). It ensures the
syscall restart process is not bypassed when changes to the cause
register occur, providing more consistent behavior across various
architectures.

For a simplified reproduction program, feel free to visit:
https://github.com/ancientmodern/riscv-ptrace-bug-demo.

Signed-off-by: Haorong Lu <ancientmodern4@gmail.com>
Link: https://lore.kernel.org/r/20230803224458.4156006-1-ancientmodern4@gmail.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Conor Dooley <conor@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2024-06-16 13:41:31 +02:00
arch riscv: signal: handle syscall restart before get_signal 2024-06-16 13:41:31 +02:00
block block: support to account io_ticks precisely 2024-06-12 11:03:07 +02:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto KEYS: asymmetric: Add missing dependencies of FIPS_SIGNATURE_SELFTEST 2024-06-12 11:02:58 +02:00
Documentation net: ena: Add dynamic recycling mechanism for rx buffers 2024-06-12 11:03:58 +02:00
drivers mmc: core: Do not force a retune before RPMB switch 2024-06-16 13:41:31 +02:00
fs afs: Don't cross .backup mountpoint from backup volume 2024-06-16 13:41:31 +02:00
include netfilter: nft_payload: move struct nft_payload_set definition where it belongs 2024-06-12 11:03:57 +02:00
init rust: make mutually exclusive with CFI_CLANG 2024-05-02 16:29:27 +02:00
io_uring io_uring: use the right type for work_llist empty check 2024-06-12 11:03:05 +02:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel bpf: Allow delete from sockmap/sockhash only if update is allowed 2024-06-12 11:03:56 +02:00
lib maple_tree: fix mas_empty_area_rev() null pointer dereference 2024-06-16 13:41:31 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm/hugetlb: fix DEBUG_LOCKS_WARN_ON(1) when dissolve_free_hugetlb_folio() 2024-05-17 11:56:24 +02:00
net netfilter: nft_fib: allow from forward/input without iif selector 2024-06-12 11:03:58 +02:00
rust rust: macros: fix soundness issue in module! macro 2024-05-17 11:56:17 +02:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-23 09:12:28 +01:00
scripts kconfig: fix comparison to constant symbols, 'm', 'n' 2024-06-12 11:03:58 +02:00
security KEYS: trusted: Do not use WARN when encode fails 2024-05-25 16:21:35 +02:00
sound ALSA: timer: Set lower bound of start tick time 2024-06-12 11:03:59 +02:00
tools bpf: Fix potential integer overflow in resolve_btfids 2024-06-12 11:03:55 +02:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Always flush async #PF workqueue when vCPU is being destroyed 2024-04-03 15:19:25 +02:00
.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 MAINTAINERS: add leah to 6.1 MAINTAINERS file 2024-05-17 11:56:16 +02:00
Makefile Linux 6.1.93 2024-06-12 11:04:00 +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.