From: Thomas Gleixner Date: Tue, 13 Jan 2009 22:36:34 +0000 (+0100) Subject: x86, vm86: fix preemption bug X-Git-Tag: firefly_0821_release~15492^2~4 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=be716615fe596ee117292dc615e95f707fb67fd1;p=firefly-linux-kernel-4.4.55.git 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: [] copy_to_user+0x33/0x108 [] save_v86_state+0x65/0x149 [] handle_vm86_trap+0x20/0x8f [] do_debug+0x15b/0x1a4 [] debug_stack_correct+0x27/0x2c [] 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 Cc: stable@kernel.org Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar --- diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 7932338d7cb3..a9e7548e1790 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