From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26EC2C433F5 for ; Fri, 11 Feb 2022 01:30:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5B1AC6B0071; Thu, 10 Feb 2022 20:30:38 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 55E876B0074; Thu, 10 Feb 2022 20:30:38 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 426986B0078; Thu, 10 Feb 2022 20:30:38 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0156.hostedemail.com [216.40.44.156]) by kanga.kvack.org (Postfix) with ESMTP id 32C316B0071 for ; Thu, 10 Feb 2022 20:30:38 -0500 (EST) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id E898C8249980 for ; Fri, 11 Feb 2022 01:30:37 +0000 (UTC) X-FDA: 79128769314.28.647E061 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) by imf09.hostedemail.com (Postfix) with ESMTP id 7B86B140009 for ; Fri, 11 Feb 2022 01:30:37 +0000 (UTC) Received: by mail-yb1-f202.google.com with SMTP id q11-20020a252a0b000000b0061e240c8fb3so12147902ybq.22 for ; Thu, 10 Feb 2022 17:30:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=RwWv/SBL/Nyi8PpdOWc2WYYolbunK2i/wwZuLVvrMdU=; b=Z4Gcf5jxsCohz3DzslMLUD9BZ0sfIvdQc/l/pfpYkaUizqSs5vQTWP9KlApyuwnYCr qy247Gemtbao51i9GOoeeVL8rOFfjxRT9wak9oSCVYh+4cQOjBAbpKIqMXGkWbt/zD09 msccdqxt52B6jGckc2BsgP1Q6P6Kp0BlzBIkCLJn+KvVbnGKDwfcRlNKv6pRFUoe+//i cTxLOD6/FMIBKG+JKDc254144JQxm1nlu+JM/ra8cOmfS9L3T911IVV6So8v11uPLwJm vZd9G/InsrCn5Gq5EHq0cTvIRB63h3F/h1SDH+GBPkwKJ3HlHxvqNMl3VpNFNPfugBUs 0cbg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=RwWv/SBL/Nyi8PpdOWc2WYYolbunK2i/wwZuLVvrMdU=; b=EW7Xa3wpSiBH8HyX6BrNufh91EiqVkzv4dIavKU9RHPn+teCf24U7qEFF6C10BDsEm 47trzDaG+IkQOQbHq96xe7uiiGPTxO5F1SEEtWjC5AwdVKPh5PPsqjfGnnfUzVJ7jy+q BCYkFOxx2H01XwYJOxuVvK5Hawd+w3SlLr+NMwUq1WWalXjSnK4sXgtLgAd5gijsW7ou 0UR49lKIuiSUgrhdrcYHaLST2Ie9t4UaCDkzZgOcCFq83uL2eKIe3+56FbsivUAfqK28 Yk8C1EXio1X0ZaWr0MyUba5VDWyTWLVpvD/uzzjkTA0j7a8JHl++0RIc+DLODLQQ8VK/ XPDQ== X-Gm-Message-State: AOAM531V3XRCRfZ4kg3QRmWK1y9GxrDdAewN8E9TNjEOicT0Y9aOl67t VFu7c1CLy/9eceQxuoWj+2p8Zrlaw4Q= X-Google-Smtp-Source: ABdhPJzj3s6SYcdRagPBA21xyaJguhhzfjpx9zuxrGEaA597KYb2tBxd2wNkgkrtJfb4pye2OSntVUn2lr4= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:cf5c:490c:4286:b6a6]) (user=surenb job=sendgmr) by 2002:a25:b98c:: with SMTP id r12mr9938344ybg.529.1644543036677; Thu, 10 Feb 2022 17:30:36 -0800 (PST) Date: Thu, 10 Feb 2022 17:30:32 -0800 Message-Id: <20220211013032.623763-1-surenb@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.35.1.265.g69c8d7142f-goog Subject: [PATCH v3 1/1] mm: fix use-after-free when anon vma name is used after vma is freed From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: ccross@google.com, sumit.semwal@linaro.org, mhocko@suse.com, dave.hansen@intel.com, keescook@chromium.org, willy@infradead.org, kirill.shutemov@linux.intel.com, vbabka@suse.cz, hannes@cmpxchg.org, ebiederm@xmission.com, brauner@kernel.org, legion@kernel.org, ran.xiaokai@zte.com.cn, sashal@kernel.org, chris.hyser@oracle.com, dave@stgolabs.net, pcc@google.com, caoxiaofeng@yulong.com, david@redhat.com, gorcunov@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com, surenb@google.com, syzbot+aa7b3d4b35f9dc46a366@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: d5a9h9w7ewy8ywwpz87mbsjcmrzf8rq7 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 7B86B140009 Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=Z4Gcf5jx; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf09.hostedemail.com: domain of 3PLwFYgYKCOEVXUHQEJRRJOH.FRPOLQXa-PPNYDFN.RUJ@flex--surenb.bounces.google.com designates 209.85.219.202 as permitted sender) smtp.mailfrom=3PLwFYgYKCOEVXUHQEJRRJOH.FRPOLQXa-PPNYDFN.RUJ@flex--surenb.bounces.google.com X-Rspam-User: X-HE-Tag: 1644543037-447941 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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->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 will result in use-after-free bug as shown below: madvise_vma_behavior << passes vma->anon_name->name as name param madvise_update_vma(name) vma_merge __vma_adjust vm_area_free <-- frees the vma replace_vma_anon_name(name) <-- UAF Fix this by raising the name refcount and stabilizing it. Introduce vma_anon_name_{get/put} API for this purpose. Fixes: 9a10064f5625 ("mm: add a field to store names for private anonymous memory") Reported-by: syzbot+aa7b3d4b35f9dc46a366@syzkaller.appspotmail.com Signed-off-by: Suren Baghdasaryan --- changes in v3: - Change madvise_vma_anon_name and replace_vma_anon_name to accept struct anon_vma_name* instead of char*, per Michal Hocko and Matthew Wilcox include/linux/mm_inline.h | 13 ++++++++ mm/madvise.c | 67 +++++++++++++++++++++++++++++---------- 2 files changed, 63 insertions(+), 17 deletions(-) diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index b725839dfe71..2ad9b28499b1 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -145,6 +145,11 @@ static __always_inline void del_page_from_lru_list(struct page *page, */ extern const char *vma_anon_name(struct vm_area_struct *vma); +/* mmap_lock should be read-locked */ +extern struct anon_vma_name *vma_anon_name_get(struct vm_area_struct *vma); + +extern void vma_anon_name_put(struct anon_vma_name *anon_name); + /* * mmap_lock should be read-locked for orig_vma->vm_mm. * mmap_lock should be write-locked for new_vma->vm_mm or new_vma should be @@ -176,6 +181,14 @@ static inline const char *vma_anon_name(struct vm_area_struct *vma) { return NULL; } + +static inline +struct anon_vma_name *vma_anon_name_get(struct vm_area_struct *vma) +{ + return NULL; +} + +static inline void vma_anon_name_put(struct anon_vma_name *anon_name) {} static inline void dup_vma_anon_name(struct vm_area_struct *orig_vma, struct vm_area_struct *new_vma) {} static inline void free_vma_anon_name(struct vm_area_struct *vma) {} diff --git a/mm/madvise.c b/mm/madvise.c index 5604064df464..1807778a5f70 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -70,6 +70,9 @@ static struct anon_vma_name *anon_vma_name_alloc(const char *name) struct anon_vma_name *anon_name; size_t count; + if (!name) + return NULL; + /* Add 1 for NUL terminator at the end of the anon_name->name */ count = strlen(name) + 1; anon_name = kmalloc(struct_size(anon_name, name, count), GFP_KERNEL); @@ -103,6 +106,23 @@ const char *vma_anon_name(struct vm_area_struct *vma) return vma->anon_name->name; } +struct anon_vma_name *vma_anon_name_get(struct vm_area_struct *vma) +{ + if (!has_vma_anon_name(vma)) + return NULL; + + mmap_assert_locked(vma->vm_mm); + + kref_get(&vma->anon_name->kref); + return vma->anon_name; +} + +void vma_anon_name_put(struct anon_vma_name *anon_name) +{ + if (anon_name) + kref_put(&anon_name->kref, vma_anon_name_free); +} + void dup_vma_anon_name(struct vm_area_struct *orig_vma, struct vm_area_struct *new_vma) { @@ -126,33 +146,34 @@ void free_vma_anon_name(struct vm_area_struct *vma) } /* mmap_lock should be write-locked */ -static int replace_vma_anon_name(struct vm_area_struct *vma, const char *name) +static int replace_vma_anon_name(struct vm_area_struct *vma, + struct anon_vma_name *anon_name) { - const char *anon_name; + const char *orig_name; - if (!name) { + if (!anon_name) { free_vma_anon_name(vma); return 0; } - anon_name = vma_anon_name(vma); - if (anon_name) { + orig_name = vma_anon_name(vma); + if (orig_name) { /* Same name, nothing to do here */ - if (!strcmp(name, anon_name)) + if (!strcmp(anon_name->name, orig_name)) return 0; free_vma_anon_name(vma); } - vma->anon_name = anon_vma_name_alloc(name); - if (!vma->anon_name) - return -ENOMEM; + kref_get(&anon_name->kref); + vma->anon_name = anon_name; return 0; } #else /* CONFIG_ANON_VMA_NAME */ -static int replace_vma_anon_name(struct vm_area_struct *vma, const char *name) +static int replace_vma_anon_name(struct vm_area_struct *vma, + struct anon_vma_name *anon_name) { - if (name) + if (anon_name) return -EINVAL; return 0; @@ -161,12 +182,15 @@ static int replace_vma_anon_name(struct vm_area_struct *vma, const char *name) /* * 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, unsigned long end, unsigned long new_flags, - const char *name) + struct anon_vma_name *anon_name) { + const char *name = anon_name ? anon_name->name : NULL; struct mm_struct *mm = vma->vm_mm; int error; pgoff_t pgoff; @@ -209,7 +233,7 @@ static int madvise_update_vma(struct vm_area_struct *vma, */ vma->vm_flags = new_flags; if (!vma->vm_file) { - error = replace_vma_anon_name(vma, name); + error = replace_vma_anon_name(vma, anon_name); if (error) return error; } @@ -976,6 +1000,7 @@ static int madvise_vma_behavior(struct vm_area_struct *vma, { int error; unsigned long new_flags = vma->vm_flags; + struct anon_vma_name *anon_name; switch (behavior) { case MADV_REMOVE: @@ -1040,8 +1065,10 @@ static int madvise_vma_behavior(struct vm_area_struct *vma, break; } + anon_name = vma_anon_name_get(vma); error = madvise_update_vma(vma, prev, start, end, new_flags, - vma_anon_name(vma)); + anon_name); + vma_anon_name_put(anon_name); out: /* @@ -1225,7 +1252,7 @@ int madvise_walk_vmas(struct mm_struct *mm, unsigned long start, static int madvise_vma_anon_name(struct vm_area_struct *vma, struct vm_area_struct **prev, unsigned long start, unsigned long end, - unsigned long name) + unsigned long anon_name) { int error; @@ -1234,7 +1261,7 @@ static int madvise_vma_anon_name(struct vm_area_struct *vma, return -EBADF; error = madvise_update_vma(vma, prev, start, end, vma->vm_flags, - (const char *)name); + (struct anon_vma_name *)anon_name); /* * madvise() returns EAGAIN if kernel resources, such as @@ -1248,8 +1275,10 @@ static int madvise_vma_anon_name(struct vm_area_struct *vma, int madvise_set_anon_name(struct mm_struct *mm, unsigned long start, unsigned long len_in, const char *name) { + struct anon_vma_name *anon_name; unsigned long end; unsigned long len; + int ret; if (start & ~PAGE_MASK) return -EINVAL; @@ -1266,8 +1295,12 @@ int madvise_set_anon_name(struct mm_struct *mm, unsigned long start, if (end == start) return 0; - return madvise_walk_vmas(mm, start, end, (unsigned long)name, + anon_name = anon_vma_name_alloc(name); + ret = madvise_walk_vmas(mm, start, end, (unsigned long)anon_name, madvise_vma_anon_name); + vma_anon_name_put(anon_name); + + return ret; } #endif /* CONFIG_ANON_VMA_NAME */ /* -- 2.35.1.265.g69c8d7142f-goog