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authorMark Rutland <mark.rutland@arm.com>2017-08-22 11:36:17 +0100
committerRussell King <rmk+kernel@armlinux.org.uk>2017-08-29 13:09:14 +0100
commit746a272e44141af24a02f6c9b0f65f4c4598ed42 (patch)
tree0f62968d884f16c92b797a75e98e286790a2ce77
parentf26fee5f111d7221b5b0724a1a54a066dc8cf410 (diff)
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ARM: 8692/1: mm: abort uaccess retries upon fatal signal
When there's a fatal signal pending, arm's do_page_fault() implementation returns 0. The intent is that we'll return to the faulting userspace instruction, delivering the signal on the way. However, if we take a fatal signal during fixing up a uaccess, this results in a return to the faulting kernel instruction, which will be instantly retried, resulting in the same fault being taken forever. As the task never reaches userspace, the signal is not delivered, and the task is left unkillable. While the task is stuck in this state, it can inhibit the forward progress of the system. To avoid this, we must ensure that when a fatal signal is pending, we apply any necessary fixup for a faulting kernel instruction. Thus we will return to an error path, and it is up to that code to make forward progress towards delivering the fatal signal. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Steve Capper <steve.capper@arm.com> Cc: stable@vger.kernel.org Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
-rw-r--r--arch/arm/mm/fault.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index ff8b0aa2dfde..42f585379e19 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -315,8 +315,11 @@ retry:
* signal first. We do not need to release the mmap_sem because
* it would already be released in __lock_page_or_retry in
* mm/filemap.c. */
- if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+ if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
+ if (!user_mode(regs))
+ goto no_context;
return 0;
+ }
/*
* Major/minor page fault accounting is only done on the