From: Nick Desaulniers <ndesaulniers@google.com>
To: Nathan Huckleberry <nhuck15@gmail.com>,
Russell King <linux@armlinux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Chunyan Zhang <zhang.lyra@gmail.com>,
clang-built-linux@googlegroups.com,
Dmitry Safonov <0x7f454c46@gmail.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org,
Lvqiang Huang <lvqiang.huang@unisoc.com>,
Matthias Brugger <matthias.bgg@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Miles Chen <miles.chen@mediatek.com>,
stable@vger.kernel.org
Subject: [PATCH 1/4] ARM: backtrace-clang: check for NULL lr
Date: Thu, 30 Jul 2020 13:51:09 -0700 [thread overview]
Message-ID: <20200730205112.2099429-2-ndesaulniers@google.com> (raw)
In-Reply-To: <20200730205112.2099429-1-ndesaulniers@google.com>
If the link register was zeroed out, do not attempt to use it for
address calculations for which there are currently no fixup handlers,
which can lead to a panic during unwind. Since panicking triggers
another unwind, this can lead to an infinite loop. If this occurs
during start_kernel(), this can prevent a kernel from booting.
commit 59b6359dd92d ("ARM: 8702/1: head-common.S: Clear lr before jumping to start_kernel()")
intentionally zeros out the link register in __mmap_switched which tail
calls into start kernel. Test for this condition so that we can stop
unwinding when initiated within start_kernel() correctly.
Cc: stable@vger.kernel.org
Fixes: commit 6dc5fd93b2f1 ("ARM: 8900/1: UNWINDER_FRAME_POINTER implementation for Clang")
Reported-by: Miles Chen <miles.chen@mediatek.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
arch/arm/lib/backtrace-clang.S | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/arm/lib/backtrace-clang.S b/arch/arm/lib/backtrace-clang.S
index 6174c45f53a5..5388ac664c12 100644
--- a/arch/arm/lib/backtrace-clang.S
+++ b/arch/arm/lib/backtrace-clang.S
@@ -144,6 +144,8 @@ for_each_frame: tst frame, mask @ Check for address exceptions
*/
1003: ldr sv_lr, [sv_fp, #4] @ get saved lr from next frame
+ tst sv_lr, #0 @ If there's no previous lr,
+ beq finished_setup @ we're done.
ldr r0, [sv_lr, #-4] @ get call instruction
ldr r3, .Lopcode+4
and r2, r3, r0 @ is this a bl call
--
2.28.0.163.g6104cc2f0b6-goog
next parent reply other threads:[~2020-07-30 20:51 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200730205112.2099429-1-ndesaulniers@google.com>
2020-07-30 20:51 ` Nick Desaulniers [this message]
2020-08-07 18:07 ` [PATCH 1/4] ARM: backtrace-clang: check for NULL lr Nathan Huckleberry
2020-07-30 20:51 ` [PATCH 2/4] ARM: backtrace-clang: add fixup for lr dereference Nick Desaulniers
2020-08-01 23:18 ` Sasha Levin
2020-08-03 18:13 ` Nick Desaulniers
2020-08-04 6:27 ` Greg KH
2020-08-06 1:24 ` Sasha Levin
2020-08-06 22:38 ` Nathan Huckleberry
2020-08-10 22:33 ` Nick Desaulniers
2020-08-20 0:13 ` Nick Desaulniers
2020-08-13 16:25 ` Sasha Levin
2020-08-19 23:56 ` Sasha Levin
2020-08-06 1:24 ` [PATCH 0/4] CONFIG_UNWINDER_FRAME_POINTER fixes+cleanups Sasha Levin
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