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

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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/
Signed-off-by: Srinivasarao Pathipati <quic_c_spathi@quicinc.com>
This commit is contained in:
Suren Baghdasaryan 2022-11-15 10:40:41 -08:00 • committed by Gerrit - the friendly Code Review server
commit 51cfccaecd
1 changed files with 6 additions and 0 deletions
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6
include/linux/mm.h
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@ -1542,6 +1542,12 @@ 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.