The patch below does not apply to the 4.2-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 589cb22bbedacf325951014c07a35a2b01ca57f6 Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon@xxxxxxx>
Date: Thu, 15 Oct 2015 13:55:53 +0100
Subject: [PATCH] arm64: compat: fix stxr failure case in SWP emulation
If the STXR instruction fails in the SWP emulation code, we leave *data
overwritten with the loaded value, therefore corrupting the data written
by a subsequent, successful attempt.
This patch re-jigs the code so that we only write back to *data once we
know that the update has happened.
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: bd35a4adc413 ("arm64: Port SWP/SWPB emulation support from arm")
Reported-by: Shengjiu Wang <shengjiu.wang@xxxxxxxxxxxxx>
Reported-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
index bcee7abac68e..937f5e58a4d3 100644
--- a/arch/arm64/kernel/armv8_deprecated.c
+++ b/arch/arm64/kernel/armv8_deprecated.c
@@ -284,21 +284,23 @@ static void register_insn_emulation_sysctl(struct ctl_table *table)
__asm__ __volatile__( \
ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, \
CONFIG_ARM64_PAN) \
- " mov %w2, %w1\n" \
- "0: ldxr"B" %w1, [%3]\n" \
- "1: stxr"B" %w0, %w2, [%3]\n" \
+ "0: ldxr"B" %w2, [%3]\n" \
+ "1: stxr"B" %w0, %w1, [%3]\n" \
" cbz %w0, 2f\n" \
" mov %w0, %w4\n" \
+ " b 3f\n" \
"2:\n" \
+ " mov %w1, %w2\n" \
+ "3:\n" \
" .pushsection .fixup,\"ax\"\n" \
" .align 2\n" \
- "3: mov %w0, %w5\n" \
- " b 2b\n" \
+ "4: mov %w0, %w5\n" \
+ " b 3b\n" \
" .popsection" \
" .pushsection __ex_table,\"a\"\n" \
" .align 3\n" \
- " .quad 0b, 3b\n" \
- " .quad 1b, 3b\n" \
+ " .quad 0b, 4b\n" \
+ " .quad 1b, 4b\n" \
" .popsection\n" \
ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, \
CONFIG_ARM64_PAN) \
--
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