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author | Oleg Nesterov <oleg@redhat.com> | 2015-03-13 09:53:09 +0100 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-03-26 13:59:47 +0100 |
commit | 4e4120654b4196c2f252dcdb5e974f16816c2939 (patch) | |
tree | 85da474712b8e23efaa01384b6c399ad1bb8962c /arch | |
parent | b90935f1d9a06d18bd7f36973556e7941104ca9a (diff) | |
download | lwn-4e4120654b4196c2f252dcdb5e974f16816c2939.tar.gz lwn-4e4120654b4196c2f252dcdb5e974f16816c2939.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>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/x86/kernel/xsave.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c index 0de1fae2bdf0..8be1e1711203 100644 --- a/arch/x86/kernel/xsave.c +++ b/arch/x86/kernel/xsave.c @@ -378,7 +378,7 @@ 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; @@ -392,14 +392,15 @@ 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(); |