Re: [tip:x86/urgent] x86: vm86: fix preemption bug

Alexander van Heukelum
2009-02-15T11:40:12Z

On Sun, 15 Feb 2009 09:36:26 GMT, "Thomas Gleixner" <tglx@linutronix.de>
said:
> Author: Thomas Gleixner <tglx@linutronix.de>
> AuthorDate: Tue, 13 Jan 2009 23:36:34 +0100
> Commit: Thomas Gleixner <tglx@linutronix.de>
> CommitDate: Sun, 15 Feb 2009 10:34:17 +0100
>
> x86: vm86: fix preemption bug
>
> commit 3d2a71a596bd9c761c8487a2178e95f8a61da083 (x86, traps: converge
> do_debug handlers) changed the preemption disable logic of do_debug()
> so vm86_handle_trap() is called with preemption disabled resulting in:
>
> BUG: sleeping function called from invalid context at
> include/linux/kernel.h:155
> in_atomic(): 1, irqs_disabled(): 0, pid: 3005, name: dosemu.bin
> Pid: 3005, comm: dosemu.bin Tainted: G W 2.6.29-rc1 #51
> Call Trace:
> [<c050d669>] copy_to_user+0x33/0x108
> [<c04181f4>] save_v86_state+0x65/0x149
> [<c0418531>] handle_vm86_trap+0x20/0x8f
> [<c064e345>] do_debug+0x15b/0x1a4
> [<c064df1f>] debug_stack_correct+0x27/0x2c
> [<c040365b>] sysenter_do_call+0x12/0x2f
> BUG: scheduling while atomic: dosemu.bin/3005/0x10000001
>
> Restore the original calling convention and reenable preemption before
> calling handle_vm86_trap().
>
> Reported-by: Michal Suchanek <hramrach@centrum.cz>
> Cc: stable@kernel.org
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: Alexander van Heukelum <heukelum@fastmail.fm>

I have no objections.

Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>

Greetings,
Alexander

> Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>
> ---
> arch/x86/kernel/traps.c | 10 +++++++++-
> 1 files changed, 9 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index 7932338..a9e7548 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -99,6 +99,12 @@ static inline void preempt_conditional_sti(struct
> pt_regs *regs)
> local_irq_enable();
> }
>
> +static inline void conditional_cli(struct pt_regs *regs)
> +{
> + if (regs->flags & X86_EFLAGS_IF)
> + local_irq_disable();
> +}
> +
> static inline void preempt_conditional_cli(struct pt_regs *regs)
> {
> if (regs->flags & X86_EFLAGS_IF)
> @@ -626,8 +632,10 @@ clear_dr7:
>
> #ifdef CONFIG_X86_32
> debug_vm86:
> + /* reenable preemption: handle_vm86_trap() might sleep */
> + dec_preempt_count();
> handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, 1);
> - preempt_conditional_cli(regs);
> + conditional_cli(regs);
> return;
> #endif
>
--
Alexander van Heukelum
heukelum@fastmail.fm

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