Messages in this thread Patch in this message | | | Date | Thu, 5 Mar 2015 20:51:49 +0100 | From | Oleg Nesterov <> | Subject | [PATCH 1/1] x86/fpu: math_state_restore() should not blindly disable irqs |
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math_state_restore() assumes it is called with irqs disabled, but this is not true if the caller is __restore_xstate_sig().
This means that if ia32_fxstate == T and __copy_from_user() fails __restore_xstate_sig() returns with irqs disabled too. This trgiggers
BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:41 [<ffffffff81381499>] dump_stack+0x59/0xa0 [<ffffffff8106bd05>] ___might_sleep+0x105/0x110 [<ffffffff8138786d>] ? _raw_spin_unlock_irqrestore+0x3d/0x70 [<ffffffff8106bd8d>] __might_sleep+0x7d/0xb0 [<ffffffff81385426>] down_read+0x26/0xa0 [<ffffffff8138788a>] ? _raw_spin_unlock_irqrestore+0x5a/0x70 [<ffffffff81136038>] print_vma_addr+0x58/0x130 [<ffffffff8100239e>] signal_fault+0xbe/0xf0 [<ffffffff810419aa>] sys32_rt_sigreturn+0xba/0xd0
Change math_state_restore() to check irqs_disabled().
Note: this is the minimal fix for -stable, it is horrible but simple. We need to rewrite math_state_restore(), init_fpu(), and cleanup their users.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: <stable@vger.kernel.org> --- arch/x86/kernel/traps.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 51c4658..7310e0e 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -774,7 +774,10 @@ void math_state_restore(void) struct task_struct *tsk = current; if (!tsk_used_math(tsk)) { - local_irq_enable(); + bool disabled = irqs_disabled(); + + if (disabled) + local_irq_enable(); /* * does a slab alloc which can sleep */ @@ -785,7 +788,9 @@ void math_state_restore(void) do_group_exit(SIGKILL); return; } - local_irq_disable(); + + if (disabled) + local_irq_disable(); } /* Avoid __kernel_fpu_begin() right after __thread_fpu_begin() */ -- 1.5.5.1
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