]> git.ipfire.org Git - thirdparty/kernel/stable.git/commit
ARM: ptrace: Restore syscall skipping for tracers
authorKees Cook <keescook@chromium.org>
Thu, 10 Aug 2023 19:54:19 +0000 (12:54 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 13 Sep 2023 07:47:57 +0000 (09:47 +0200)
commitc0e71cb3ae9d195421dbb74164fbc286b27f5809
tree6590afc266858fc54bdafcd0ded8f82b2b27e281
parent9d75837cedb9a433f0243aaf64a66cdf7b77b113
ARM: ptrace: Restore syscall skipping for tracers

[ Upstream commit 4697b5848bd933f68ebd04836362c8de0cacaf71 ]

Since commit 4e57a4ddf6b0 ("ARM: 9107/1: syscall: always store
thread_info->abi_syscall"), the seccomp selftests "syscall_errno"
and "syscall_faked" have been broken. Both seccomp and PTRACE depend
on using the special value of "-1" for skipping syscalls. This value
wasn't working because it was getting masked by __NR_SYSCALL_MASK in
both PTRACE_SET_SYSCALL and get_syscall_nr().

Explicitly test for -1 in PTRACE_SET_SYSCALL and get_syscall_nr(),
leaving it exposed when present, allowing tracers to skip syscalls
again.

Cc: Russell King <linux@armlinux.org.uk>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org
Fixes: 4e57a4ddf6b0 ("ARM: 9107/1: syscall: always store thread_info->abi_syscall")
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20230810195422.2304827-2-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
arch/arm/include/asm/syscall.h
arch/arm/kernel/ptrace.c