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zsmalloc: correct fragile [kmap|kunmap]_atomic use 

The kunmap_atomic should use virtual address getting by kmap_atomic.
However, some pieces of code in zsmalloc uses modified address, not the
one got by kmap_atomic for kunmap_atomic.

It's okay for working because zsmalloc modifies the address inner
PAGE_SIZE bounday so it works with current kmap_atomic's implementation.
But it's still fragile with potential changing of kmap_atomic so let's
correct it.

I got a subtle bug when I implemented a new feature of zsmalloc
(compaction) due to a link's mishandling (the link was over page
boundary).  Although it was totally my mistake, it took a while to find
the cause because an unpredictable kmapped address was unmapped causing an
almost random crash.

Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Minchan Kim 2014-12-12 16:56:58 -08:00 committed by Linus Torvalds
parent b1b00a5b8a
commit af4ee5e977
1 changed files with 12 additions and 9 deletions
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21
mm/zsmalloc.c
View File

@ -629,6 +629,7 @@ static void init_zspage(struct page *first_page, struct size_class *class)
struct page *next_page;
struct link_free *link;
unsigned int i = 1;
void *vaddr;
/*
* page->index stores offset of first object starting
@ -639,8 +640,8 @@ static void init_zspage(struct page *first_page, struct size_class *class)
if (page != first_page)
page->index = off;
link = (struct link_free *)kmap_atomic(page) +
off / sizeof(*link);
vaddr = kmap_atomic(page);
link = (struct link_free *)vaddr + off / sizeof(*link);
while ((off += class->size) < PAGE_SIZE) {
link->next = obj_location_to_handle(page, i++);
@ -654,7 +655,7 @@ static void init_zspage(struct page *first_page, struct size_class *class)
*/
next_page = get_next_page(page);
link->next = obj_location_to_handle(next_page, 0);
kunmap_atomic(link);
kunmap_atomic(vaddr);
page = next_page;
off %= PAGE_SIZE;
}
@ -1064,6 +1065,7 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
unsigned long obj;
struct link_free *link;
struct size_class *class;
void *vaddr;
struct page *first_page, *m_page;
unsigned long m_objidx, m_offset;
@ -1092,11 +1094,11 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
obj_handle_to_location(obj, &m_page, &m_objidx);
m_offset = obj_idx_to_offset(m_page, m_objidx, class->size);
link = (struct link_free *)kmap_atomic(m_page) +
m_offset / sizeof(*link);
vaddr = kmap_atomic(m_page);
link = (struct link_free *)vaddr + m_offset / sizeof(*link);
first_page->freelist = link->next;
memset(link, POISON_INUSE, sizeof(*link));
kunmap_atomic(link);
kunmap_atomic(vaddr);
first_page->inuse++;
/* Now move the zspage to another fullness group, if required */
@ -1112,6 +1114,7 @@ void zs_free(struct zs_pool *pool, unsigned long obj)
struct link_free *link;
struct page *first_page, *f_page;
unsigned long f_objidx, f_offset;
void *vaddr;
int class_idx;
struct size_class *class;
@ -1130,10 +1133,10 @@ void zs_free(struct zs_pool *pool, unsigned long obj)
spin_lock(&class->lock);
/* Insert this object in containing zspage's freelist */
link = (struct link_free *)((unsigned char *)kmap_atomic(f_page)
+ f_offset);
vaddr = kmap_atomic(f_page);
link = (struct link_free *)(vaddr + f_offset);
link->next = first_page->freelist;
kunmap_atomic(link);
kunmap_atomic(vaddr);
first_page->freelist = (void *)obj;
first_page->inuse--;