Star64_linux/arch/x86/kernel/fpu
Andrei Vagin b2479ab426 x86/fpu: Stop relying on userspace for info to fault in xsave buffer
commit d877550eaf2dc9090d782864c96939397a3c6835 upstream.

Before this change, the expected size of the user space buffer was
taken from fx_sw->xstate_size. fx_sw->xstate_size can be changed
from user-space, so it is possible construct a sigreturn frame where:

 * fx_sw->xstate_size is smaller than the size required by valid bits in
   fx_sw->xfeatures.
 * user-space unmaps parts of the sigrame fpu buffer so that not all of
   the buffer required by xrstor is accessible.

In this case, xrstor tries to restore and accesses the unmapped area
which results in a fault. But fault_in_readable succeeds because buf +
fx_sw->xstate_size is within the still mapped area, so it goes back and
tries xrstor again. It will spin in this loop forever.

Instead, fault in the maximum size which can be touched by XRSTOR (taken
from fpstate->user_size).

[ dhansen: tweak subject / changelog ]

Fixes: fcb3635f50 ("x86/fpu/signal: Handle #PF in the direct restore path")
Reported-by: Konstantin Bogomolov <bogomolov@google.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrei Vagin <avagin@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc:stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240130063603.3392627-1-avagin%40google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-02-23 09:25:10 +01:00
..
bugs.c x86/fpu: Replace the includes of fpu/internal.h 2021-10-20 15:27:29 +02:00
context.h x86/fpu: Invalidate FPU state correctly on exec() 2023-08-24 11:01:45 +02:00
core.c x86/fpu: Allow caller to constrain xfeatures when copying to uabi buffer 2023-10-12 11:08:58 -04:00
init.c x86/fpu: Mark init functions __init 2023-06-16 10:16:01 +02:00
internal.h x86/fpu/signal: Prepare for variable sigframe length 2021-10-26 10:18:09 +02:00
legacy.h x86/fpu: Remove .fixup usage 2021-12-11 09:09:48 +01:00
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
regset.c x86: Add PTRACE interface for shadow stack 2023-08-02 15:01:51 -07:00
signal.c x86/fpu: Stop relying on userspace for info to fault in xsave buffer 2024-02-23 09:25:10 +01:00
xstate.c KVM: x86: Constrain guest-supported xfeatures only at KVM_GET_XSAVE{2} 2023-10-12 11:08:58 -04:00
xstate.h x86/fpu: Allow caller to constrain xfeatures when copying to uabi buffer 2023-10-12 11:08:58 -04:00