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authorMark Rutland <mark.rutland@arm.com>2017-07-11 14:19:22 (GMT)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-09-02 05:07:53 (GMT)
commit509d8b52bbe7e6f6022a086989e7ecf5180508cc (patch)
tree912e4cc41ad17cac66b46b2e3b25b8b28dcbfef8
parent3e033635b2b7eab01855c5a3e426e364064fd12b (diff)
downloadlinux-509d8b52bbe7e6f6022a086989e7ecf5180508cc.tar.xz
arm64: mm: abort uaccess retries upon fatal signal
commit 289d07a2dc6c6b6f3e4b8a62669320d99dbe6c3d upstream. When there's a fatal signal pending, arm64'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. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Laura Abbott <labbott@redhat.com> Reviewed-by: Steve Capper <steve.capper@arm.com> Tested-by: Steve Capper <steve.capper@arm.com> Reviewed-by: James Morse <james.morse@arm.com> Tested-by: James Morse <james.morse@arm.com> Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/arm64/mm/fault.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 0e90c7e0..fec5b1c 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -373,8 +373,11 @@ 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 initial