From: Will Deacon Date: Thu, 15 Oct 2015 12:55:53 +0000 (+0100) Subject: arm64: compat: fix stxr failure case in SWP emulation X-Git-Tag: Ubuntu-5.2.0-15.16~10442^2~3 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=589cb22bbedacf325951014c07a35a2b01ca57f6;p=mirror_ubuntu-eoan-kernel.git 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: Fixes: bd35a4adc413 ("arm64: Port SWP/SWPB emulation support from arm") Reported-by: Shengjiu Wang Reported-by: Vladimir Murzin Signed-off-by: Will Deacon --- 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) \