Patch "arm64: fault: Route pte translation faults via do_translation_fault" has been added to the 4.4-stable tree
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This is a note to let you know that I've just added the patch titled
arm64: fault: Route pte translation faults via do_translation_fault
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-fault-route-pte-translation-faults-via-do_translation_fault.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
Quoted 1 line
From
760bfb47c36a07741a089bf6a28e854ffbee7dc9Mon Sep 17 00:00:00 2001
From: Will Deacon <[email protected]>
Date: Fri, 29 Sep 2017 12:27:41 +0100
Subject: arm64: fault: Route pte translation faults via do_translation_fault
From: Will Deacon <[email protected]>
commit 760bfb47c36a07741a089bf6a28e854ffbee7dc9 upstream.
We currently route pte translation faults via do_page_fault, which elides the address check against TASK_SIZE before invoking the mm fault handling code. However, this can cause issues with the path walking code in conjunction with our word-at-a-time implementation because load_unaligned_zeropad can end up faulting in kernel space if it reads across a page boundary and runs into a page fault (e.g. by attempting to read from a guard region).
In the case of such a fault, load_unaligned_zeropad has registered a fixup to shift the valid data and pad with zeroes, however the abort is reported as a level 3 translation fault and we dispatch it straight to do_page_fault, despite it being a kernel address. This results in calling a sleeping function from atomic context:
BUG: sleeping function called from invalid context at arch/arm64/mm/fault.c:313 in_atomic(): 0, irqs_disabled(): 0, pid: 10290 Internal error: Oops - BUG: 0 [#1] PREEMPT SMP [...] [<ffffff8e016cd0cc>] ___might_sleep+0x134/0x144 [<ffffff8e016cd158>] __might_sleep+0x7c/0x8c [<ffffff8e016977f0>] do_page_fault+0x140/0x330 [<ffffff8e01681328>] do_mem_abort+0x54/0xb0 Exception stack(0xfffffffb20247a70 to 0xfffffffb20247ba0) [...] [<ffffff8e016844fc>] el1_da+0x18/0x78 [<ffffff8e017f399c>] path_parentat+0x44/0x88 [<ffffff8e017f4c9c>] filename_parentat+0x5c/0xd8 [<ffffff8e017f5044>] filename_create+0x4c/0x128 [<ffffff8e017f59e4>] SyS_mkdirat+0x50/0xc8 [<ffffff8e01684e30>] el0_svc_naked+0x24/0x28 Code: 36380080 d5384100 f9400800 9402566d (d4210000) ---[ end trace 2d01889f2bca9b9f ]---
Fix this by dispatching all translation faults to do_translation_faults, which avoids invoking the page fault logic for faults on kernel addresses.
--- arch/arm64/mm/fault.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
arch/arm64/mm/fault.c +1 -1
@@ -447,7 +447,7 @@ static struct fault_info { { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 0 translation fault" }, { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 1 translation fault" }, { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 2 translation fault" }, - { do_page_fault, SIGSEGV, SEGV_MAPERR, "level 3 translation fault" }, + { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 3 translation fault" }, { do_bad, SIGBUS, 0, "unknown 8" }, { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 access flag fault" }, { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 access flag fault" },
Patches currently in stable-queue which might be from [email protected] are
queue-4.4/arm64-fault-route-pte-translation-faults-via-do_translation_fault.patch queue-4.4/arm64-make-sure-spsel-is-always-set.patch