From: vjitta@codeaurora.org
To: akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Cc: vjitta@codeaurora.org, vinmenon@codeaurora.org
Subject: [PATCH] mm: vmalloc: Prevent use after free in _vm_unmap_aliases
Date: Thu, 18 Mar 2021 15:38:25 +0530 [thread overview]
Message-ID: <1616062105-23263-1-git-send-email-vjitta@codeaurora.org> (raw)
From: Vijayanand Jitta <vjitta@codeaurora.org>
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.
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>
---
mm/vmalloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index d5f2a84..ebb6f57 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1762,7 +1762,7 @@ 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;
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
2.7.4
next reply other threads:[~2021-03-18 10:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-18 10:08 vjitta [this message]
2021-03-18 16:59 ` [PATCH] mm: vmalloc: Prevent use after free in _vm_unmap_aliases Uladzislau Rezki
2021-03-24 3:29 ` Vijayanand Jitta
2021-03-24 13:32 ` Uladzislau Rezki
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