Commit 4080ef15 authored by Lorenzo Stoakes's avatar Lorenzo Stoakes Committed by Andrew Morton
Browse files

mm: unconditionally close VMAs on error 

Incorrect invocation of VMA callbacks when the VMA is no longer in a
consistent state is bug prone and risky to perform.

With regards to the important vm_ops->close() callback We have gone to
great lengths to try to track whether or not we ought to close VMAs.

Rather than doing so and risking making a mistake somewhere, instead
unconditionally close and reset vma->vm_ops to an empty dummy operations
set with a NULL .close operator.

We introduce a new function to do so - vma_close() - and simplify existing
vms logic which tracked whether we needed to close or not.

This simplifies the logic, avoids incorrect double-calling of the .close()
callback and allows us to update error paths to simply call vma_close()
unconditionally - making VMA closure idempotent.

Link: https://lkml.kernel.org/r/28e89dda96f68c505cb6f8e9fc9b57c3e9f74b42.1730224667.git.lorenzo.stoakes@oracle.com


Fixes: deb0f656 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
Signed-off-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reported-by: default avatarJann Horn <jannh@google.com>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: default avatarJann Horn <jannh@google.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Helge Deller <deller@gmx.de>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 3dd6ed34

mm/internal.h

+18 −0
Original line number Diff line number Diff line
@@ -135,6 +135,24 @@ static inline int mmap_file(struct file *file, struct vm_area_struct *vma) 
	return err;

}



/*

 * If the VMA has a close hook then close it, and since closing it might leave

 * it in an inconsistent state which makes the use of any hooks suspect, clear

 * them down by installing dummy empty hooks.

 */

static inline void vma_close(struct vm_area_struct *vma)

{

	if (vma->vm_ops && vma->vm_ops->close) {

		vma->vm_ops->close(vma);



		/*

		 * The mapping is in an inconsistent state, and no further hooks

		 * may be invoked upon it.

		 */

		vma->vm_ops = &vma_dummy_vm_ops;

	}

}



#ifdef CONFIG_MMU



/* Flags for folio_pte_batch(). */

mm/mmap.c

+2 −3
Original line number Diff line number Diff line
@@ -1573,8 +1573,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, 
	return addr;



close_and_free_vma:

	if (file && !vms.closed_vm_ops && vma->vm_ops && vma->vm_ops->close)

		vma->vm_ops->close(vma);

	vma_close(vma);



	if (file || vma->vm_file) {

unmap_and_free_vma:
@@ -1934,7 +1933,7 @@ void exit_mmap(struct mm_struct *mm) 
	do {

		if (vma->vm_flags & VM_ACCOUNT)

			nr_accounted += vma_pages(vma);

		remove_vma(vma, /* unreachable = */ true, /* closed = */ false);

		remove_vma(vma, /* unreachable = */ true);

		count++;

		cond_resched();

		vma = vma_next(&vmi);

mm/nommu.c

+1 −2
Original line number Diff line number Diff line
@@ -589,8 +589,7 @@ static int delete_vma_from_mm(struct vm_area_struct *vma) 
 */

static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)

{

	if (vma->vm_ops && vma->vm_ops->close)

		vma->vm_ops->close(vma);

	vma_close(vma);

	if (vma->vm_file)

		fput(vma->vm_file);

	put_nommu_region(vma->vm_region);

mm/vma.c

+5 −9
Original line number Diff line number Diff line
@@ -323,11 +323,10 @@ static bool can_vma_merge_right(struct vma_merge_struct *vmg, 
/*

 * Close a vm structure and free it.

 */

void remove_vma(struct vm_area_struct *vma, bool unreachable, bool closed)

void remove_vma(struct vm_area_struct *vma, bool unreachable)

{

	might_sleep();

	if (!closed && vma->vm_ops && vma->vm_ops->close)

		vma->vm_ops->close(vma);

	vma_close(vma);

	if (vma->vm_file)

		fput(vma->vm_file);

	mpol_put(vma_policy(vma));
@@ -1115,9 +1114,7 @@ void vms_clean_up_area(struct vma_munmap_struct *vms, 
	vms_clear_ptes(vms, mas_detach, true);

	mas_set(mas_detach, 0);

	mas_for_each(mas_detach, vma, ULONG_MAX)

		if (vma->vm_ops && vma->vm_ops->close)

			vma->vm_ops->close(vma);

	vms->closed_vm_ops = true;

		vma_close(vma);

}



/*
@@ -1160,7 +1157,7 @@ void vms_complete_munmap_vmas(struct vma_munmap_struct *vms, 
	/* Remove and clean up vmas */

	mas_set(mas_detach, 0);

	mas_for_each(mas_detach, vma, ULONG_MAX)

		remove_vma(vma, /* = */ false, vms->closed_vm_ops);

		remove_vma(vma, /* unreachable = */ false);



	vm_unacct_memory(vms->nr_accounted);

	validate_mm(mm);
@@ -1684,8 +1681,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, 
	return new_vma;



out_vma_link:

	if (new_vma->vm_ops && new_vma->vm_ops->close)

		new_vma->vm_ops->close(new_vma);

	vma_close(new_vma);



	if (new_vma->vm_file)

		fput(new_vma->vm_file);

mm/vma.h

+1 −3
Original line number Diff line number Diff line
@@ -42,7 +42,6 @@ struct vma_munmap_struct { 
	int vma_count;                  /* Number of vmas that will be removed */

	bool unlock;                    /* Unlock after the munmap */

	bool clear_ptes;                /* If there are outstanding PTE to be cleared */

	bool closed_vm_ops;		/* call_mmap() was encountered, so vmas may be closed */

	/* 1 byte hole */

	unsigned long nr_pages;         /* Number of pages being removed */

	unsigned long locked_vm;        /* Number of locked pages */
@@ -198,7 +197,6 @@ static inline void init_vma_munmap(struct vma_munmap_struct *vms, 
	vms->unmap_start = FIRST_USER_ADDRESS;

	vms->unmap_end = USER_PGTABLES_CEILING;

	vms->clear_ptes = false;

	vms->closed_vm_ops = false;

}

#endif
@@ -269,7 +267,7 @@ int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm, 
		  unsigned long start, size_t len, struct list_head *uf,

		  bool unlock);



void remove_vma(struct vm_area_struct *vma, bool unreachable, bool closed);

void remove_vma(struct vm_area_struct *vma, bool unreachable);



void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,

		struct vm_area_struct *prev, struct vm_area_struct *next);