From f0861f49bd946ff94fce4f82509c45e167f63690 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Borys=20Pop=C5=82awski?= Date: Wed, 5 Oct 2022 00:59:03 +0200 Subject: [PATCH 1/2] x86/sgx: Add overflow check in sgx_validate_offset_length() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit sgx_validate_offset_length() function verifies "offset" and "length" arguments provided by userspace, but was missing an overflow check on their addition. Add it. Fixes: c6d26d370767 ("x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES") Signed-off-by: Borys Popławski Signed-off-by: Borislav Petkov Reviewed-by: Jarkko Sakkinen Cc: stable@vger.kernel.org # v5.11+ Link: https://lore.kernel.org/r/0d91ac79-6d84-abed-5821-4dbe59fa1a38@invisiblethingslab.com --- arch/x86/kernel/cpu/sgx/ioctl.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c index ebe79d60619f..da8b8ea6b063 100644 --- a/arch/x86/kernel/cpu/sgx/ioctl.c +++ b/arch/x86/kernel/cpu/sgx/ioctl.c @@ -356,6 +356,9 @@ static int sgx_validate_offset_length(struct sgx_encl *encl, if (!length || !IS_ALIGNED(length, PAGE_SIZE)) return -EINVAL; + if (offset + length < offset) + return -EINVAL; + if (offset + length - PAGE_SIZE >= encl->size) return -EINVAL; From 36b038791e1e2baea892e9276588815fd14894b4 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Thu, 10 Nov 2022 12:44:00 +0000 Subject: [PATCH 2/2] x86/fpu: Drop fpregs lock before inheriting FPU permissions Mike Galbraith reported the following against an old fork of preempt-rt but the same issue also applies to the current preempt-rt tree. BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: systemd preempt_count: 1, expected: 0 RCU nest depth: 0, expected: 0 Preemption disabled at: fpu_clone CPU: 6 PID: 1 Comm: systemd Tainted: G E (unreleased) Call Trace: dump_stack_lvl ? fpu_clone __might_resched rt_spin_lock fpu_clone ? copy_thread ? copy_process ? shmem_alloc_inode ? kmem_cache_alloc ? kernel_clone ? __do_sys_clone ? do_syscall_64 ? __x64_sys_rt_sigprocmask ? syscall_exit_to_user_mode ? do_syscall_64 ? syscall_exit_to_user_mode ? do_syscall_64 ? syscall_exit_to_user_mode ? do_syscall_64 ? exc_page_fault ? entry_SYSCALL_64_after_hwframe Mike says: The splat comes from fpu_inherit_perms() being called under fpregs_lock(), and us reaching the spin_lock_irq() therein due to fpu_state_size_dynamic() returning true despite static key __fpu_state_size_dynamic having never been enabled. Mike's assessment looks correct. fpregs_lock on a PREEMPT_RT kernel disables preemption so calling spin_lock_irq() in fpu_inherit_perms() is unsafe. This problem exists since commit 9e798e9aa14c ("x86/fpu: Prepare fpu_clone() for dynamically enabled features"). Even though the original bug report should not have enabled the paths at all, the bug still exists. fpregs_lock is necessary when editing the FPU registers or a task's FP state but it is not necessary for fpu_inherit_perms(). The only write of any FP state in fpu_inherit_perms() is for the new child which is not running yet and cannot context switch or be borrowed by a kernel thread yet. Hence, fpregs_lock is not protecting anything in the new child until clone() completes and can be dropped earlier. The siglock still needs to be acquired by fpu_inherit_perms() as the read of the parent's permissions has to be serialised. [ bp: Cleanup splat. ] Fixes: 9e798e9aa14c ("x86/fpu: Prepare fpu_clone() for dynamically enabled features") Reported-by: Mike Galbraith Signed-off-by: Mel Gorman Signed-off-by: Borislav Petkov Reviewed-by: Thomas Gleixner Cc: Link: https://lore.kernel.org/r/20221110124400.zgymc2lnwqjukgfh@techsingularity.net --- arch/x86/kernel/fpu/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 3b28c5b25e12..d00db56a8868 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -605,9 +605,9 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal) if (test_thread_flag(TIF_NEED_FPU_LOAD)) fpregs_restore_userregs(); save_fpregs_to_fpstate(dst_fpu); + fpregs_unlock(); if (!(clone_flags & CLONE_THREAD)) fpu_inherit_perms(dst_fpu); - fpregs_unlock(); /* * Children never inherit PASID state.