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Michael Ellerman e41d6c3f4f powerpc/signal64: Copy siginfo before changing regs->nip 
In commit 96d7a4e06f ("powerpc/signal64: Rewrite handle_rt_signal64()
to minimise uaccess switches") the 64-bit signal code was rearranged to
use user_write_access_begin/end().

As part of that change the call to copy_siginfo_to_user() was moved
later in the function, so that it could be done after the
user_write_access_end().

In particular it was moved after we modify regs->nip to point to the
signal trampoline. That means if copy_siginfo_to_user() fails we exit
handle_rt_signal64() with an error but with regs->nip modified, whereas
previously we would not modify regs->nip until the copy succeeded.

Returning an error from signal delivery but with regs->nip updated
leaves the process in a sort of half-delivered state. We do immediately
force a SEGV in signal_setup_done(), called from do_signal(), so the
process should never run in the half-delivered state.

However that SEGV is not delivered until we've gone around to
do_notify_resume() again, so it's possible some tracing could observe
the half-delivered state.

There are other cases where we fail signal delivery with regs partly
updated, eg. the write to newsp and SA_SIGINFO, but the latter at least
is very unlikely to fail as it reads back from the frame we just wrote
to.

Looking at other arches they seem to be more careful about leaving regs
unchanged until the copy operations have succeeded, and in general that
seems like good hygenie.

So although the current behaviour is not cleary buggy, it's also not
clearly correct. So move the call to copy_siginfo_to_user() up prior to
the modification of regs->nip, which is closer to the old behaviour, and
easier to reason about.

Fixes: 96d7a4e06f ("powerpc/signal64: Rewrite handle_rt_signal64() to minimise uaccess switches")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210608134605.2783677-1-mpe@ellerman.id.au
2021-06-14 22:14:54 +10:00
arch powerpc/signal64: Copy siginfo before changing regs->nip 2021-06-14 22:14:54 +10:00
block block-5.13-2021-05-14 2021-05-15 08:52:30 -07:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto for-5.13/drivers-2021-04-27 2021-04-28 14:39:37 -07:00
Documentation powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and scv syscalls 2021-05-21 00:58:03 +10:00
drivers Driver core fixes for 5.13-rc2 2021-05-16 10:13:14 -07:00
fs Merge branch 'akpm' (patches from Andrew) 2021-05-15 09:42:27 -07:00
include Driver core fixes for 5.13-rc2 2021-05-16 10:13:14 -07:00
init Merge branch 'akpm' (patches from Andrew) 2021-05-07 00:34:51 -07:00
ipc ipc/sem.c: spelling fix 2021-05-07 00:26:34 -07:00
kernel Two fixes for timers: 2021-05-16 09:42:13 -07:00
lib kasan: fix unit tests with CONFIG_UBSAN_LOCAL_BOUNDS enabled 2021-05-14 19:41:32 -07:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm mm/ioremap: fix iomap_max_page_shift 2021-05-14 19:41:32 -07:00
net mm: fix struct page layout on 32-bit systems 2021-05-14 19:41:32 -07:00
samples Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
scripts Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
security trusted-keys: match tpm_get_ops on all return paths 2021-05-12 22:36:37 +03:00
sound sound fixes for 5.13-rc1 2021-05-07 11:40:18 -07:00
tools powerpc/64s/syscall: Use pt_regs.trap to distinguish syscall ABI difference between sc and scv syscalls 2021-05-21 00:58:03 +10:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt kvm: Cap halt polling at kvm->max_halt_poll_ns 2021-05-07 06:06:22 -04:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.cocciconfig
.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 .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap Merge drm/drm-fixes into drm-misc-fixes 2021-05-11 13:35:52 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
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 libnvdimm fixes for 5.13-rc2 2021-05-15 08:32:51 -07:00
Makefile Linux 5.13-rc2 2021-05-16 15:27:44 -07:00
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.