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| author | Vijayanand Jitta <vjitta@codeaurora.org> | 2021-04-30 08:59:07 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-04-30 21:20:40 +0300 |
| commit | ad216c0316ad6391d90f4de0a7f59396b2925a06 (patch) | |
| tree | 478afea7154377d038c9e306bb737292b986d9ac /mm | |
| parent | d70bec8cc95ad32f6b7e3e6fad72acdd3a5418e9 (diff) | |
| download | linux-ad216c0316ad6391d90f4de0a7f59396b2925a06.tar.xz | |
mm: vmalloc: prevent use after free in _vm_unmap_aliases
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@codeaurora.org
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/vmalloc.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 612a3790cfd4..51874a341ab0 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2040,7 +2040,7 @@ 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; |