Commit-ID: 827409b2f5b58573ae3774fe6bd2d6daeb335878 Gitweb: http://git.kernel.org/tip/827409b2f5b58573ae3774fe6bd2d6daeb335878 Author: Ingo Molnar <mingo@xxxxxxxxxx> AuthorDate: Wed, 27 May 2015 12:22:29 +0200 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Sat, 22 Aug 2015 10:23:03 +0200 x86/fpu/math-emu: Fix crash in fork() During later stages of math-emu bootup the following crash triggers: math_emulate: 0060:c100d0a8 Kernel panic - not syncing: Math emulation needed in kernel CPU: 0 PID: 1511 Comm: login Not tainted 4.2.0-rc7+ #1012 [...] Call Trace: [<c181d50d>] dump_stack+0x41/0x52 [<c181c918>] panic+0x77/0x189 [<c1003530>] ? math_error+0x140/0x140 [<c164c2d7>] math_emulate+0xba7/0xbd0 [<c100d0a8>] ? fpu__copy+0x138/0x1c0 [<c1109c3c>] ? __alloc_pages_nodemask+0x12c/0x870 [<c136ac20>] ? proc_clear_tty+0x40/0x70 [<c136ac6e>] ? session_clear_tty+0x1e/0x30 [<c1003530>] ? math_error+0x140/0x140 [<c1003575>] do_device_not_available+0x45/0x70 [<c100d0a8>] ? fpu__copy+0x138/0x1c0 [<c18258e6>] error_code+0x5a/0x60 [<c1003530>] ? math_error+0x140/0x140 [<c100d0a8>] ? fpu__copy+0x138/0x1c0 [<c100c205>] arch_dup_task_struct+0x25/0x30 [<c1048cea>] copy_process.part.51+0xea/0x1480 [<c115a8e5>] ? dput+0x175/0x200 [<c136af70>] ? no_tty+0x30/0x30 [<c1157242>] ? do_vfs_ioctl+0x322/0x540 [<c104a21a>] _do_fork+0xca/0x340 [<c1057b06>] ? SyS_rt_sigaction+0x66/0x90 [<c104a557>] SyS_clone+0x27/0x30 [<c1824a80>] sysenter_do_call+0x12/0x12 The reason is the incorrect assumption in fpu_copy(), that FNSAVE can be executed from math-emu kernels as well. Don't try to copy the registers, the soft state will be copied by fork anyway, so the child task inherits the parent task's soft math state. With this fix applied math-emu kernels boot up fine on modern hardware and the 'no387 nofxsr' boot options. Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Bobby Powers <bobbypowers@xxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Brian Gerst <brgerst@xxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/kernel/fpu/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 79de954..d25097c 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -270,7 +270,7 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu) dst_fpu->fpregs_active = 0; dst_fpu->last_cpu = -1; - if (src_fpu->fpstate_active) + if (src_fpu->fpstate_active && cpu_has_fpu) fpu_copy(dst_fpu, src_fpu); return 0; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|