From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 1/2] arm64: fix dump_instr when PAN and UAO are in use
Date: Mon, 13 Jun 2016 13:48:24 +0100 [thread overview]
Message-ID: <20160613124823.GF1605@arm.com> (raw)
In-Reply-To: <1465812915-19801-2-git-send-email-mark.rutland@arm.com>
On Mon, Jun 13, 2016 at 11:15:14AM +0100, Mark Rutland wrote:
> If the kernel is set to show unhandled signals, and a user task does not
> handle a SIGILL as a result of an instruction abort, we will attempt to
> log the offending instruction with dump_instr before killing the task.
>
> We use dump_instr to log the encoding of the offending userspace
> instruction. However, dump_instr is also used to dump instructions from
> kernel space, and internally always switches to KERNEL_DS before dumping
> the instruction with get_user. When both PAN and UAO are in use, reading
> a user instruction via get_user while in KERNEL_DS will result in a
> permission fault, which leads to an Oops.
>
> As we have regs corresponding to the context of the original instruction
> abort, we can inspect this and only flip to KERNEL_DS if the original
> abort was taken from the kernel, avoiding this issue. At the same time,
> remove the redundant (and incorrect) comments regarding the order
> dump_mem and dump_instr are called in.
>
> Signed-off-by: Mark Rutland <mark.rutland@arm•com>
> Reported-by: Vladimir Murzin <vladimir.murzin@arm•com>
> Cc: Catalin Marinas <catalin.marinas@arm•com>
> Cc: James Morse <james.morse@arm•com>
> Cc: Robin Murphy <robin.murphy@arm•com>
> Cc: Will Deacon <will.deacon@arm•com>
> Fixes: 57f4959bad0a154a ("arm64: kernel: Add support for User Access Override")
> ---
> arch/arm64/kernel/traps.c | 26 +++++++++++++-------------
> 1 file changed, 13 insertions(+), 13 deletions(-)
Queued as a fix for 4.8 w/ Vladimir's Tested-by. Please try to keep fixes
and cleanups/features separate in future series.
Will
next prev parent reply other threads:[~2016-06-13 12:48 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-13 10:15 [PATCH 0/2] arm64: traps.c fix + cleanup Mark Rutland
2016-06-13 10:15 ` [PATCH 1/2] arm64: fix dump_instr when PAN and UAO are in use Mark Rutland
2016-06-13 12:15 ` Vladimir Murzin
2016-06-13 12:48 ` Will Deacon [this message]
2016-06-13 12:54 ` Mark Rutland
2016-06-13 10:15 ` [PATCH 2/2] arm64: simplify dump_mem Mark Rutland
2016-06-21 14:48 ` Catalin Marinas
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