diff options
| author | Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> | 2013-09-10 18:44:42 +0530 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2013-09-11 11:39:37 +1000 |
| commit | 69e044dd759e26667c110ab771d2c908fbd5d3dd (patch) | |
| tree | bdd11f7c23fc8472e025f133b283c7cc322ada32 | |
| parent | 256588fda10f2a712631f8a4e72641a66adebdb8 (diff) | |
| download | linux-69e044dd759e26667c110ab771d2c908fbd5d3dd.tar.bz2 | |
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.c | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 76d8e7cc7805..2dd69bf4af46 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)) |