Commit 577d50d9 authored Nov 15, 2022 by Suren Baghdasaryan Committed by Srinivasarao Pathipati Mar 14, 2023

ANDROID: mm: assert that mmap_lock is taken exclusively in vm_write_begin



vm_write_{begin|end} has to be called when mmap_lock is taken
exlusively. Add an assert statement in vm_write_begin to enforce
that. free_pgtables can free page tables without exclusive mmap_lock
if the vma was isolated, therefore avoid assertions in such cases.

Bug: 257443051
Change-Id: Ie81aefe025c743cda6f66717d2f08f4d78a55608
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Git-commit: d65d4a0538c3511eb02fed4b628e3588715c90d8
Git-repo: https://android.googlesource.com/kernel/common/


[quic_c_spathi@quicinc.com: fix build error]
Signed-off-by: Srinivasarao Pathipati <quic_c_spathi@quicinc.com>

parent cb88a76c

include/linux/mm.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -1498,6 +1498,12 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
		#ifdef CONFIG_SPECULATIVE_PAGE_FAULT
		static inline void vm_write_begin(struct vm_area_struct *vma)
		{
		/*
		* Isolated vma might be freed without exclusive mmap_lock but
		* speculative page fault handler still needs to know it was changed.
		*/
		if (!RB_EMPTY_NODE(&vma->vm_rb))
		WARN_ON_ONCE(!rwsem_is_locked(&(vma->vm_mm)->mmap_sem));
		/*
		* The reads never spins and preemption
		* disablement is not required.