path: root/arch/arm64/mm
diff options
authorMark Rutland <mark.rutland@arm.com>2017-07-11 15:19:22 +0100
committerWill Deacon <will.deacon@arm.com>2017-08-22 18:15:42 +0100
commit289d07a2dc6c6b6f3e4b8a62669320d99dbe6c3d (patch)
treeb2e3d5317f654c4bc1bacfff4c16c5d9431199a5 /arch/arm64/mm
parentarm64: fpsimd: Prevent registers leaking across exec (diff)
arm64: mm: abort uaccess retries upon fatal signal
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> Cc: stable@vger.kernel.org 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>
Diffstat (limited to 'arch/arm64/mm')
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 2509e4fe6992..1f22a41565a3 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -435,8 +435,11 @@ retry:
* the mmap_sem because it would already be released
* in __lock_page_or_retry in mm/filemap.c.
- if (fatal_signal_pending(current))
+ if (fatal_signal_pending(current)) {
+ if (!user_mode(regs))
+ goto no_context;
return 0;
+ }
* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of