From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 517897E for ; Sat, 5 Mar 2022 04:28:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 13555C340F1; Sat, 5 Mar 2022 04:28:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1646454539; bh=st98WjUsllA+87j/BxRW1JSdxLeAXWCwiNeCFZRRKq8=; h=Date:To:From:In-Reply-To:Subject:From; b=glwQFlbzJnU1oaGfY3AYSJU1JWvG8wSWiek+QWcdXQFv+hCIxlNdJa3WFYf2awO6/ 3HqJK3p+SdYdRj9zwLtwJX7hXTp+GcrLc8cWvX5dMMCLYDHjCQA06G6+Hl4HA6mDB9 R2BBoejaqwuyyCjgJ0j4gQku7/FFiBOkI8GyUnGc= Date: Fri, 04 Mar 2022 20:28:58 -0800 To: willy@infradead.org,vbabka@suse.cz,sumit.semwal@linaro.org,sashal@kernel.org,pcc@google.com,mhocko@suse.com,legion@kernel.org,kirill.shutemov@linux.intel.com,keescook@chromium.org,hannes@cmpxchg.org,gorcunov@gmail.com,ebiederm@xmission.com,david@redhat.com,dave@stgolabs.net,dave.hansen@intel.com,chris.hyser@oracle.com,ccross@google.com,caoxiaofeng@yulong.com,brauner@kernel.org,surenb@google.com,akpm@linux-foundation.org,patches@lists.linux.dev,linux-mm@kvack.org,mm-commits@vger.kernel.org,torvalds@linux-foundation.org,akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220304202822.d47f8084928321c83070d7d7@linux-foundation.org> Subject: [patch 4/8] mm: fix use-after-free when anon vma name is used after vma is freed Message-Id: <20220305042859.13555C340F1@smtp.kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: From: Suren Baghdasaryan Subject: mm: fix use-after-free when anon vma name is used after vma is freed When adjacent vmas are being merged it can result in the vma that was originally passed to madvise_update_vma being destroyed. In the current implementation, the name parameter passed to madvise_update_vma points directly to vma->anon_name and it is used after the call to vma_merge. In the cases when vma_merge merges the original vma and destroys it, this might result in UAF. For that the original vma would have to hold the anon_vma_name with the last reference. The following vma would need to contain a different anon_vma_name object with the same string. Such scenario is shown below: madvise_vma_behavior(vma) madvise_update_vma(vma, ..., anon_name == vma->anon_name) vma_merge(vma) __vma_adjust(vma) <-- merges vma with adjacent one vm_area_free(vma) <-- frees the original vma replace_vma_anon_name(anon_name) <-- UAF of vma->anon_name Fix this by raising the name refcount and stabilizing it. Link: https://lkml.kernel.org/r/20220224231834.1481408-3-surenb@google.com Link: https://lkml.kernel.org/r/20220223153613.835563-3-surenb@google.com Fixes: 9a10064f5625 ("mm: add a field to store names for private anonymous memory") Signed-off-by: Suren Baghdasaryan Reported-by: syzbot+aa7b3d4b35f9dc46a366@syzkaller.appspotmail.com Acked-by: Michal Hocko Cc: Alexey Gladkov Cc: Chris Hyser Cc: Christian Brauner Cc: Colin Cross Cc: Cyrill Gorcunov Cc: Dave Hansen Cc: David Hildenbrand Cc: Davidlohr Bueso Cc: "Eric W. Biederman" Cc: Johannes Weiner Cc: Kees Cook Cc: "Kirill A. Shutemov" Cc: Matthew Wilcox Cc: Michal Hocko Cc: Peter Collingbourne Cc: Sasha Levin Cc: Sumit Semwal Cc: Vlastimil Babka Cc: Xiaofeng Cao Signed-off-by: Andrew Morton --- mm/madvise.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/mm/madvise.c~mm-fix-use-after-free-when-anon-vma-name-is-used-after-vma-is-freed +++ a/mm/madvise.c @@ -131,6 +131,8 @@ static int replace_anon_vma_name(struct /* * Update the vm_flags on region of a vma, splitting it or merging it as * necessary. Must be called with mmap_sem held for writing; + * Caller should ensure anon_name stability by raising its refcount even when + * anon_name belongs to a valid vma because this function might free that vma. */ static int madvise_update_vma(struct vm_area_struct *vma, struct vm_area_struct **prev, unsigned long start, @@ -945,6 +947,7 @@ static int madvise_vma_behavior(struct v unsigned long behavior) { int error; + struct anon_vma_name *anon_name; unsigned long new_flags = vma->vm_flags; switch (behavior) { @@ -1010,8 +1013,11 @@ static int madvise_vma_behavior(struct v break; } + anon_name = anon_vma_name(vma); + anon_vma_name_get(anon_name); error = madvise_update_vma(vma, prev, start, end, new_flags, - anon_vma_name(vma)); + anon_name); + anon_vma_name_put(anon_name); out: /* _