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author | Minchan Kim <minchan@kernel.org> | 2014-12-12 16:56:58 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-12-13 12:42:50 -0800 |
commit | af4ee5e977acb150371c28bd85cb7e34cac48b13 (patch) | |
tree | 67463f79cabacffded1af15a140e8e8030502c41 /mm/zsmalloc.c | |
parent | b1b00a5b8a6cf32e3973507decf1216709b55072 (diff) | |
download | linux-af4ee5e977acb150371c28bd85cb7e34cac48b13.tar.gz linux-af4ee5e977acb150371c28bd85cb7e34cac48b13.tar.bz2 linux-af4ee5e977acb150371c28bd85cb7e34cac48b13.zip |
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>
Diffstat (limited to 'mm/zsmalloc.c')
-rw-r--r-- | mm/zsmalloc.c | 21 |
1 files changed, 12 insertions, 9 deletions
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 5481c677e465..83ecdb675c40 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -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--; |