mm: vmalloc: prevent use after free in _vm_unmap_aliases
mainline inclusion from mainline-5.13-rc1 commit ad216c03 category: bugfix bugzilla: 57119 https://gitee.com/openeuler/kernel/issues/I4DDEL Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad216c0316ad6391d90f4de0a7f59396b2925a06 ------------------------------------------------- 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.orgSigned-off-by: NVijayanand Jitta <vjitta@codeaurora.org> Reviewed-by: NUladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org> (cherry picked from commit ad216c03) Signed-off-by: NYue Zou <zouyue3@huawei.com> Reviewed-by: NChen Wandun <chenwandun@huawei.com> Signed-off-by: NChen Jun <chenjun102@huawei.com> Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
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