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mm/vmalloc: fix wrong behavior in vread 

commit f608788cd2 ("mm/vmalloc: use rb_tree instead of list for vread()
lookups") use rb_tree instread of list to speed up lookup, but function
__find_vmap_area is try to find a vmap_area that include target address,
if target address is smaller than the leftmost node in vmap_area_root, it
will return NULL, then vread will read nothing.  This behavior is
different from the primitive semantics.

The correct way is find the first vmap_are that bigger than target addr,
that is what function find_vmap_area_exceed_addr does.

Link: https://lkml.kernel.org/r/20210714015959.3204871-1-chenwandun@huawei.com
Fixes: f608788cd2 ("mm/vmalloc: use rb_tree instead of list for vread() lookups")
Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Reported-by: Hulk Robot <hulkci@huawei.com>
Cc: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Chen Wandun 2021-09-02 14:57:26 -07:00 committed by Linus Torvalds
parent f8bcbecfb6
commit f181234a5a
1 changed files with 28 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
mm/vmalloc.c
View File

@ -787,6 +787,28 @@ unsigned long vmalloc_nr_pages(void)
return atomic_long_read(&nr_vmalloc_pages);
}
static struct vmap_area *find_vmap_area_exceed_addr(unsigned long addr)
{
struct vmap_area *va = NULL;
struct rb_node *n = vmap_area_root.rb_node;
while (n) {
struct vmap_area *tmp;
tmp = rb_entry(n, struct vmap_area, rb_node);
if (tmp->va_end > addr) {
va = tmp;
if (tmp->va_start <= addr)
break;
n = n->rb_left;
} else
n = n->rb_right;
}
return va;
}
static struct vmap_area *__find_vmap_area(unsigned long addr)
{
struct rb_node *n = vmap_area_root.rb_node;
@ -3287,9 +3309,14 @@ long vread(char *buf, char *addr, unsigned long count)
count = -(unsigned long) addr;
spin_lock(&vmap_area_lock);
va = __find_vmap_area((unsigned long)addr);
va = find_vmap_area_exceed_addr((unsigned long)addr);
if (!va)
goto finished;
/* no intersects with alive vmap_area */
if ((unsigned long)addr + count <= va->va_start)
goto finished;
list_for_each_entry_from(va, &vmap_area_list, list) {
if (!count)
break;