Messages in this thread Patch in this message | | | Date | Sat, 7 Mar 2015 16:38:44 +0100 | From | Oleg Nesterov <> | Subject | [PATCH 1/1] x86/fpu: x86/fpu: avoid math_state_restore() without used_math() in __restore_xstate_sig() |
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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 trgiggers
BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:41 [<ffffffff81381499>] dump_stack+0x59/0xa0 [<ffffffff8106bd05>] ___might_sleep+0x105/0x110 [<ffffffff8138786d>] ? _raw_spin_unlock_irqrestore+0x3d/0x70 [<ffffffff8106bd8d>] __might_sleep+0x7d/0xb0 [<ffffffff81385426>] down_read+0x26/0xa0 [<ffffffff8138788a>] ? _raw_spin_unlock_irqrestore+0x5a/0x70 [<ffffffff81136038>] print_vma_addr+0x58/0x130 [<ffffffff8100239e>] signal_fault+0xbe/0xf0 [<ffffffff810419aa>] sys32_rt_sigreturn+0xba/0xd0
Change __restore_xstate_sig() to call set_used_math() unconditionally, this avoids sti/cli 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> Cc: <stable@vger.kernel.org> --- 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 de9dcf8..dff0ec2 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(); -- 1.5.5.1
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