From: Vijayanand Jitta
mainline inclusion
from mainline-5.13-rc1
commit ad216c0316ad6391d90f4de0a7f59396b2925a06
category: bugfix
issue: #I3ZXZF
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
-------------------------------------------------
A potential use after free can occur in _vm_unmap_aliases where an already
freed vmap_area could be accessed, Consider the following scenario:
Process 1 Process 2
__vm_unmap_aliases __vm_unmap_aliases
purge_fragmented_blocks_allcpus rcu_read_lock()
rcu_read_lock()
list_del_rcu(&vb->free_list)
list_for_each_entry_rcu(vb .. )
__purge_vmap_area_lazy
kmem_cache_free(va)
va_start = vb->va->va_start
Here Process 1 is in purge path and it does list_del_rcu on vmap_block and
later frees the vmap_area, since Process 2 was holding the rcu lock at
this time vmap_block will still be present in and Process 2 accesse it and
thereby it tries to access vmap_area of that vmap_block which was already
freed by Process 1 and this results in use after free.
Fix this by adding a check for vb->dirty before accessing vmap_area
structure since vb->dirty will be set to VMAP_BBMAP_BITS in purge path
checking for this will prevent the use after free.
Link: https://lkml.kernel.org/r/1616062105-23263-1-git-send-email-vjitta@codeauror...
Signed-off-by: Vijayanand Jitta
Reviewed-by: Uladzislau Rezki (Sony)
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
(cherry picked from commit ad216c0316ad6391d90f4de0a7f59396b2925a06)
Signed-off-by: Yue Zou
Reviewed-by: Chen Wandun
Signed-off-by: Chen Jun
Signed-off-by: Yu Changchun
---
mm/vmalloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index fff03a331314..c1243e0dac83 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1746,7 +1746,7 @@ static void _vm_unmap_aliases(unsigned long start, unsigned long end, int flush)
rcu_read_lock();
list_for_each_entry_rcu(vb, &vbq->free, free_list) {
spin_lock(&vb->lock);
- if (vb->dirty) {
+ if (vb->dirty && vb->dirty != VMAP_BBMAP_BITS) {
unsigned long va_start = vb->va->va_start;
unsigned long s, e;
--
2.22.0
