Thomas Gleixner 2e4d4123c8 x86/fpu: Prevent FPU state corruption ... commit 59f5ede3bc upstream. The FPU usage related to task FPU management is either protected by disabling interrupts (switch_to, return to user) or via fpregs_lock() which is a wrapper around local_bh_disable(). When kernel code wants to use the FPU then it has to check whether it is possible by calling irq_fpu_usable(). But the condition in irq_fpu_usable() is wrong. It allows FPU to be used when: !in_interrupt() || interrupted_user_mode() || interrupted_kernel_fpu_idle() The latter is checking whether some other context already uses FPU in the kernel, but if that's not the case then it allows FPU to be used unconditionally even if the calling context interrupted a fpregs_lock() critical region. If that happens then the FPU state of the interrupted context becomes corrupted. Allow in kernel FPU usage only when no other context has in kernel FPU usage and either the calling context is not hard interrupt context or the hard interrupt did not interrupt a local bottomhalf disabled region. It's hard to find a proper Fixes tag as the condition was broken in one way or the other for a very long time and the eager/lazy FPU changes caused a lot of churn. Picked something remotely connected from the history. This survived undetected for quite some time as FPU usage in interrupt context is rare, but the recent changes to the random code unearthed it at least on a kernel which had FPU debugging enabled. There is probably a higher rate of silent corruption as not all issues can be detected by the FPU debugging code. This will be addressed in a subsequent change. Fixes: 5d2bd7009f ("x86, fpu: decouple non-lazy/eager fpu restore from xsave") Reported-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: Borislav Petkov <bp@suse.de> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220501193102.588689270@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-05-12 12:30:02 +02:00
..
bugs.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
core.c	x86/fpu: Prevent FPU state corruption	2022-05-12 12:30:02 +02:00
init.c	x86/fpu: Get rid of fpu__get_supported_xfeatures_mask()	2021-06-23 17:49:46 +02:00
Makefile	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
regset.c	x86/ptrace: Fix xfpregs_set()'s incorrect xmm clearing	2022-03-02 11:47:47 +01:00
signal.c	gup: Turn fault_in_pages_{readable,writeable} into fault_in_{readable,writeable}	2022-05-01 17:22:28 +02:00
xstate.c	x86/fpu/xstate: Clear xstate header in copy_xstate_to_uabi_buf() again	2021-06-24 17:19:51 +02:00