This is a note to let you know that I've just added the patch titled

perf/callchain: Force USER_DS when invoking perf_callchain_user()

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: perf-callchain-force-user_ds-when-invoking-perf_callchain_user.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Mon Apr 9 17:09:24 CEST 2018

From: Will Deacon will.deacon@arm.com Date: Tue, 9 May 2017 18:00:04 +0100 Subject: perf/callchain: Force USER_DS when invoking perf_callchain_user()

From: Will Deacon will.deacon@arm.com

[ Upstream commit 88b0193d9418c00340e45e0a913a0813bc6c8c96 ]

Perf can generate and record a user callchain in response to a synchronous request, such as a tracepoint firing. If this happens under set_fs(KERNEL_DS), then we can end up walking the user stack (and dereferencing/saving whatever we find there) without the protections usually afforded by checks such as access_ok.

Rather than play whack-a-mole with each architecture's stack unwinding implementation, fix the root of the problem by ensuring that we force USER_DS when invoking perf_callchain_user from the perf core.

Reported-by: Al Viro viro@ZenIV.linux.org.uk Signed-off-by: Will Deacon will.deacon@arm.com Acked-by: Peter Zijlstra peterz@infradead.org Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Arnaldo Carvalho de Melo acme@redhat.com Cc: Jiri Olsa jolsa@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Thomas Gleixner tglx@linutronix.de Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/events/callchain.c | 6 ++++++ 1 file changed, 6 insertions(+)

--- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -227,12 +227,18 @@ get_perf_callchain(struct pt_regs *regs, }

if (regs) { + mm_segment_t fs; + if (crosstask) goto exit_put;

if (add_mark) perf_callchain_store_context(&ctx, PERF_CONTEXT_USER); + + fs = get_fs(); + set_fs(USER_DS); perf_callchain_user(&ctx, regs); + set_fs(fs); } }

Patches currently in stable-queue which might be from will.deacon@arm.com are

queue-4.9/perf-callchain-force-user_ds-when-invoking-perf_callchain_user.patch queue-4.9/arm64-pci-fix-struct-acpi_pci_root_ops-allocation-failure-path.patch queue-4.9/arm64-perf-ignore-exclude_hv-when-kernel-is-running-in-hyp.patch queue-4.9/arm64-kernel-restrict-dev-mem-read-calls-to-linear-region.patch queue-4.9/arm64-futex-fix-undefined-behaviour-with-futex_op_oparg_shift-usage.patch