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Commit17c2895("arm64: Abstract syscallno manipulation") abstracts out the pt_regs.syscallno value for a syscall cancelled by a tracer as NO_SYSCALL, and provides helpers to set and check for this condition. However, the way this was implemented has the unintended side-effect of disabling part of the syscall restart logic. This comes about because the second in_syscall() check in do_signal() re-evaluates the "in a syscall" condition based on the updated pt_regs instead of the original pt_regs. forget_syscall() is explicitly called prior to the second check in order to prevent restart logic in the ret_to_user path being spuriously triggered, which means that the second in_syscall() check always yields false. This triggers a failure in tools/testing/selftests/seccomp/seccomp_bpf.c, when using ptrace to suppress a signal that interrups a nanosleep() syscall. Misbehaviour of this type is only expected in the case where a tracer suppresses a signal and the target process is either being single-stepped or the interrupted syscall attempts to restart via -ERESTARTBLOCK. This patch restores the old behaviour by performing the in_syscall() check only once at the start of the function. Fixes:17c2895860("arm64: Abstract syscallno manipulation") Signed-off-by: Dave Martin <Dave.Martin@arm.com> Reported-by: Sumit Semwal <sumit.semwal@linaro.org> Cc: Will Deacon <will.deacon@arm.com> Cc: <stable@vger.kernel.org> # 4.14.x- Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.