Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 7cf5d821 authored by Lee Jones's avatar Lee Jones
Browse files

Revert "Revert "mm/rmap: Fix anon_vma->degree ambiguity leading to double-reuse"" 



This reverts commit 4f35cec76058557d9eaec0d501d03c7657eb56b4 and does so
in an abi-safe way.

This is done by adding the new fields only to the end of the structure
and this structure is only passed around to other functions as a
pointer, the internal structure layout is only touched by the core
kernel, so adding it to the end is safe.

ABI differences manually updated:

Leaf changes summary: 1 artifact changed
Changed leaf types summary: 1 leaf type changed
Removed/Changed/Added functions summary: 0 Removed, 0 Changed, 0 Added function
Removed/Changed/Added variables summary: 0 Removed, 0 Changed, 0 Added variable

'struct anon_vma at rmap.h:29:1' changed:
  type size changed from 704 to 832 (in bits)
  2 data member insertions:
    'unsigned long int num_children', at offset 704 (in bits) at rmap.h:70:1
    'unsigned long int num_active_vmas', at offset 768 (in bits) at rmap.h:72:1
  761 impacted interfaces

Bug: 260678056
Bug: 253167854
Change-Id: Ib1d45625cbc2e0b21330ca3dc2aa7aff34666d31
Signed-off-by: default avatarLee Jones <joneslee@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@google.com>
(cherry picked from commit d3e1a50cba092fa9c56fc642ee74f360c4b40a17)
parent 5c92efb6

android/abi_gki_aarch64.xml

+1729 −1725

File changed.

Preview size limit exceeded, changes collapsed.

include/linux/rmap.h

+20 −7
Original line number Diff line number Diff line
@@ -38,13 +38,7 @@ struct anon_vma { 
	 */

	atomic_t refcount;



	/*

	 * Count of child anon_vmas and VMAs which points to this anon_vma.

	 *

	 * This counter is used for making decision about reusing anon_vma

	 * instead of forking new one. See comments in function anon_vma_clone.

	 */

	unsigned degree;

	unsigned degree;		/* ANDROID: KABI preservation, DO NOT USE! */



	struct anon_vma *parent;	/* Parent of this anon_vma */
@@ -59,6 +53,25 @@ struct anon_vma { 


	/* Interval tree of private "related" vmas */

	struct rb_root_cached rb_root;



	/*

	 * ANDROID: KABI preservation, it's safe to put these at the end of this structure as it's

	 * only passed by a pointer everywhere, the size and internal structures are local to the

	 * core kernel.

	 */

#ifndef __GENKSYMS__

	/*

	 * Count of child anon_vmas. Equals to the count of all anon_vmas that

	 * have ->parent pointing to this one, including itself.

	 *

	 * This counter is used for making decision about reusing anon_vma

	 * instead of forking new one. See comments in function anon_vma_clone.

	 */

	unsigned long num_children;

	/* Count of VMAs whose ->anon_vma pointer points to this object. */

	unsigned long num_active_vmas;

#endif



};



/*

mm/rmap.c

+18 −14
Original line number Diff line number Diff line
@@ -82,7 +82,8 @@ static inline struct anon_vma *anon_vma_alloc(void) 
	anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);

	if (anon_vma) {

		atomic_set(&anon_vma->refcount, 1);

		anon_vma->degree = 1;	/* Reference for first vma */

		anon_vma->num_children = 0;

		anon_vma->num_active_vmas = 0;

		anon_vma->parent = anon_vma;

		/*

		 * Initialise the anon_vma root to point to itself. If called
@@ -190,6 +191,7 @@ int __anon_vma_prepare(struct vm_area_struct *vma) 
		anon_vma = anon_vma_alloc();

		if (unlikely(!anon_vma))

			goto out_enomem_free_avc;

		anon_vma->num_children++; /* self-parent link for new root */

		allocated = anon_vma;

	}
@@ -199,8 +201,7 @@ int __anon_vma_prepare(struct vm_area_struct *vma) 
	if (likely(!vma->anon_vma)) {

		vma->anon_vma = anon_vma;

		anon_vma_chain_link(vma, avc, anon_vma);

		/* vma reference or self-parent link for new root */

		anon_vma->degree++;

		anon_vma->num_active_vmas++;

		allocated = NULL;

		avc = NULL;

	}
@@ -279,19 +280,19 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) 
		anon_vma_chain_link(dst, avc, anon_vma);



		/*

		 * Reuse existing anon_vma if its degree lower than two,

		 * that means it has no vma and only one anon_vma child.

		 * Reuse existing anon_vma if it has no vma and only one

		 * anon_vma child.

		 *

		 * Do not chose parent anon_vma, otherwise first child

		 * will always reuse it. Root anon_vma is never reused:

		 * Root anon_vma is never reused:

		 * it has self-parent reference and at least one child.

		 */

		if (!dst->anon_vma && anon_vma != src->anon_vma &&

				anon_vma->degree < 2)

		if (!dst->anon_vma && src->anon_vma &&

		    anon_vma->num_children < 2 &&

		    anon_vma->num_active_vmas == 0)

			dst->anon_vma = anon_vma;

	}

	if (dst->anon_vma)

		dst->anon_vma->degree++;

		dst->anon_vma->num_active_vmas++;

	unlock_anon_vma_root(root);

	return 0;
@@ -341,6 +342,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) 
	anon_vma = anon_vma_alloc();

	if (!anon_vma)

		goto out_error;

	anon_vma->num_active_vmas++;

	avc = anon_vma_chain_alloc(GFP_KERNEL);

	if (!avc)

		goto out_error_free_anon_vma;
@@ -361,7 +363,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) 
	vma->anon_vma = anon_vma;

	anon_vma_lock_write(anon_vma);

	anon_vma_chain_link(vma, avc, anon_vma);

	anon_vma->parent->degree++;

	anon_vma->parent->num_children++;

	anon_vma_unlock_write(anon_vma);



	return 0;
@@ -393,7 +395,7 @@ void unlink_anon_vmas(struct vm_area_struct *vma) 
		 * to free them outside the lock.

		 */

		if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) {

			anon_vma->parent->degree--;

			anon_vma->parent->num_children--;

			continue;

		}
@@ -401,7 +403,8 @@ void unlink_anon_vmas(struct vm_area_struct *vma) 
		anon_vma_chain_free(avc);

	}

	if (vma->anon_vma)

		vma->anon_vma->degree--;

		vma->anon_vma->num_active_vmas--;



	unlock_anon_vma_root(root);



	/*
@@ -412,7 +415,8 @@ void unlink_anon_vmas(struct vm_area_struct *vma) 
	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {

		struct anon_vma *anon_vma = avc->anon_vma;



		VM_WARN_ON(anon_vma->degree);

		VM_WARN_ON(anon_vma->num_children);

		VM_WARN_ON(anon_vma->num_active_vmas);

		put_anon_vma(anon_vma);



		list_del(&avc->same_vma);