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authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>2013-09-10 18:44:42 +0530
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2013-09-11 11:39:37 +1000
commit69e044dd759e26667c110ab771d2c908fbd5d3dd (patch)
treebdd11f7c23fc8472e025f133b283c7cc322ada32
parent256588fda10f2a712631f8a4e72641a66adebdb8 (diff)
downloadop-kernel-dev-69e044dd759e26667c110ab771d2c908fbd5d3dd.zip
op-kernel-dev-69e044dd759e26667c110ab771d2c908fbd5d3dd.tar.gz
powerpc: Fix possible deadlock on page fault
stack_grow_into/14082 is trying to acquire lock: (&mm->mmap_sem){++++++}, at: [<c000000000206d28>] .might_fault+0x78/0xe0 but task is already holding lock: (&mm->mmap_sem){++++++}, at: [<c0000000007ffd8c>] .do_page_fault+0x24c/0x910 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&mm->mmap_sem); lock(&mm->mmap_sem); *** DEADLOCK *** May be due to missing lock nesting notation 1 lock held by stack_grow_into/14082: #0: (&mm->mmap_sem){++++++}, at: [<c0000000007ffd8c>] .do_page_fault+0x24c/0x910 stack backtrace: CPU: 21 PID: 14082 Comm: stack_grow_into Not tainted 3.10.0-10.el7.ppc64.debug #1 Call Trace: [c0000003d396b850] [c000000000016e7c] .show_stack+0x7c/0x1f0 (unreliable) [c0000003d396b920] [c000000000813fc8] .dump_stack+0x28/0x3c [c0000003d396b990] [c000000000124b90] .__lock_acquire+0x1640/0x1800 [c0000003d396bab0] [c00000000012570c] .lock_acquire+0xac/0x250 [c0000003d396bb80] [c000000000206d54] .might_fault+0xa4/0xe0 [c0000003d396bbf0] [c0000000007ffe2c] .do_page_fault+0x2ec/0x910 [c0000003d396be30] [c0000000000092e8] handle_page_fault+0x10/0x30 Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
-rw-r--r--arch/powerpc/mm/fault.c13
1 files changed, 10 insertions, 3 deletions
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 76d8e7c..2dd69bf 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -206,7 +206,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
int trap = TRAP(regs);
int is_exec = trap == 0x400;
int fault;
- int rc = 0;
+ int rc = 0, store_update_sp = 0;
#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
/*
@@ -280,6 +280,14 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
+ /*
+ * We want to do this outside mmap_sem, because reading code around nip
+ * can result in fault, which will cause a deadlock when called with
+ * mmap_sem held
+ */
+ if (user_mode(regs))
+ store_update_sp = store_updates_sp(regs);
+
/* When running in the kernel we expect faults to occur only to
* addresses in user space. All other faults represent errors in the
* kernel and should generate an OOPS. Unfortunately, in the case of an
@@ -345,8 +353,7 @@ retry:
* between the last mapped region and the stack will
* expand the stack rather than segfaulting.
*/
- if (address + 2048 < uregs->gpr[1]
- && (!user_mode(regs) || !store_updates_sp(regs)))
+ if (address + 2048 < uregs->gpr[1] && !store_update_sp)
goto bad_area;
}
if (expand_stack(vma, address))
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