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;a=summary
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@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Mon Apr 9 17:09:24 CEST 2018
From: Will Deacon <will.deacon@xxxxxxx>
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@xxxxxxx>
[ 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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxx 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