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Date: Mon, 14 May 2012 22:11:41 -0400 From: Paul Gortmaker <paul.gortmaker@...driver.com> To: <stable@...nel.org>, <linux-kernel@...r.kernel.org> Subject: [34-longterm 005/179] powerpc/kexec: Fix memory corruption from unallocated slaves From: Milton Miller <miltonm@....com> ------------------- This is a commit scheduled for the next v2.6.34 longterm release. http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git If you see a problem with using this for longterm, please comment. ------------------- commit 3d2cea732d68aa270c360f55d8669820ebce188a upstream. Commit 1fc711f7ffb01089efc58042cfdbac8573d1b59a (powerpc/kexec: Fix race in kexec shutdown) moved the write to signal the cpu had exited the kernel from before the transition to real mode in kexec_smp_wait to kexec_wait. Unfornately it missed that kexec_wait is used both by cpus leaving the kernel and by secondary slave cpus that were not allocated a paca for what ever reason -- they could be beyond nr_cpus or not described in the current device tree for whatever reason (for example, kexec-load was not refreshed after a cpu hotplug operation). Cpus coming through that path they will write to paca[NR_CPUS] which is beyond the space allocated for the paca data and overwrite memory not allocated to pacas but very likely still real mode accessable). Move the write back to kexec_smp_wait, which is used only by cpus that found their paca, but after the transition to real mode. Signed-off-by: Milton Miller <miltonm@....com> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org> Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com> --- arch/powerpc/kernel/misc_64.S | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S index a2b18df..9161338 100644 --- a/arch/powerpc/kernel/misc_64.S +++ b/arch/powerpc/kernel/misc_64.S @@ -463,7 +463,8 @@ _GLOBAL(disable_kernel_fp) * wait for the flag to change, indicating this kernel is going away but * the slave code for the next one is at addresses 0 to 100. * - * This is used by all slaves. + * This is used by all slaves, even those that did not find a matching + * paca in the secondary startup code. * * Physical (hardware) cpu id should be in r3. */ @@ -472,10 +473,6 @@ _GLOBAL(kexec_wait) 1: mflr r5 addi r5,r5,kexec_flag-1b - li r4,KEXEC_STATE_REAL_MODE - stb r4,PACAKEXECSTATE(r13) - SYNC - 99: HMT_LOW #ifdef CONFIG_KEXEC /* use no memory without kexec */ lwz r4,0(r5) @@ -500,11 +497,17 @@ kexec_flag: * * get phys id from paca * switch to real mode + * mark the paca as no longer used * join other cpus in kexec_wait(phys_id) */ _GLOBAL(kexec_smp_wait) lhz r3,PACAHWCPUID(r13) bl real_mode + + li r4,KEXEC_STATE_REAL_MODE + stb r4,PACAKEXECSTATE(r13) + SYNC + b .kexec_wait /* -- 1.7.9.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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