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authorOleg Nesterov <oleg@redhat.com>2015-03-13 09:53:09 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-03-26 15:01:00 +0100
commit1e6d9ee06210b979bca6f4d3a1e1d663e0bc5bcb (patch)
treee50e33dd1d7a52bd5e3c9cd933b471364a746fb3
parent31c06b946ce68c0792288f456f0e57e45c19b322 (diff)
downloadlwn-1e6d9ee06210b979bca6f4d3a1e1d663e0bc5bcb.tar.gz
lwn-1e6d9ee06210b979bca6f4d3a1e1d663e0bc5bcb.zip
x86/fpu: Avoid math_state_restore() without used_math() in __restore_xstate_sig()
commit a7c80ebcac3068b1c3cb27d538d29558c30010c8 upstream. 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 triggers: BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:41 dump_stack ___might_sleep ? _raw_spin_unlock_irqrestore __might_sleep down_read ? _raw_spin_unlock_irqrestore print_vma_addr signal_fault sys32_rt_sigreturn Change __restore_xstate_sig() to call set_used_math() unconditionally. This avoids enabling and disabling interrupts in math_state_restore(). If copy_from_user() fails, we can simply do fpu_finit() by hand. [ Note: this is only the first step. math_state_restore() should not check used_math(), it should set this flag. While init_fpu() should simply die. ] Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Pekka Riikonen <priikone@iki.fi> Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com> Cc: Rik van Riel <riel@redhat.com> Cc: Suresh Siddha <sbsiddha@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150307153844.GB25954@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/kernel/xsave.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 1ee723298e90..92f37e7683c5 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -376,7 +376,7 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
* thread's fpu state, reconstruct fxstate from the fsave
* header. Sanitize the copied state etc.
*/
- struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
+ struct fpu *fpu = &tsk->thread.fpu;
struct user_i387_ia32_struct env;
int err = 0;
@@ -390,14 +390,15 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
*/
drop_fpu(tsk);
- if (__copy_from_user(xsave, buf_fx, state_size) ||
+ if (__copy_from_user(&fpu->state->xsave, buf_fx, state_size) ||
__copy_from_user(&env, buf, sizeof(env))) {
+ fpu_finit(fpu);
err = -1;
} else {
sanitize_restored_xstate(tsk, &env, xstate_bv, fx_only);
- set_used_math();
}
+ set_used_math();
if (use_eager_fpu()) {
preempt_disable();
math_state_restore();