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[173.164.112.133]) by smtp.gmail.com with ESMTPSA id u195sm9156481pgb.64.2018.01.10.18.09.39 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Jan 2018 18:09:45 -0800 (PST) From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Kees Cook , David Windsor , Boaz Harrosh , Linus Torvalds , Alexander Viro , Andrew Morton , Andy Lutomirski , Christoph Hellwig , Christoph Lameter , "David S. Miller" , Laura Abbott , Mark Rutland , "Martin K. Petersen" , Paolo Bonzini , Christian Borntraeger , Christoffer Dall , Dave Kleikamp , Jan Kara , Luis de Bethencourt , Marc Zyngier , Rik van Riel , Matthew Garrett , linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, netdev@vger.kernel.org, linux-mm@kvack.org, kernel-hardening@lists.openwall.com Subject: [PATCH 17/38] exofs: Define usercopy region in exofs_inode_cache slab cache Date: Wed, 10 Jan 2018 18:02:49 -0800 Message-Id: <1515636190-24061-18-git-send-email-keescook@chromium.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1515636190-24061-1-git-send-email-keescook@chromium.org> References: <1515636190-24061-1-git-send-email-keescook@chromium.org> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: David Windsor The exofs short symlink names, stored in struct exofs_i_info.i_data and therefore contained in the exofs_inode_cache slab cache, need to be copied to/from userspace. cache object allocation: fs/exofs/super.c: exofs_alloc_inode(...): ... oi = kmem_cache_alloc(exofs_inode_cachep, GFP_KERNEL); ... return &oi->vfs_inode; fs/exofs/namei.c: exofs_symlink(...): ... inode->i_link = (char *)oi->i_data; example usage trace: readlink_copy+0x43/0x70 vfs_readlink+0x62/0x110 SyS_readlinkat+0x100/0x130 fs/namei.c: readlink_copy(..., link): ... copy_to_user(..., link, len); (inlined in vfs_readlink) generic_readlink(dentry, ...): struct inode *inode = d_inode(dentry); const char *link = inode->i_link; ... readlink_copy(..., link); In support of usercopy hardening, this patch defines a region in the exofs_inode_cache slab cache in which userspace copy operations are allowed. This region is known as the slab cache's usercopy region. Slab caches can now check that each dynamically sized copy operation involving cache-managed memory falls entirely within the slab's usercopy region. This patch is modified from Brad Spengler/PaX Team's PAX_USERCOPY whitelisting code in the last public patch of grsecurity/PaX based on my understanding of the code. Changes or omissions from the original code are mine and don't reflect the original grsecurity/PaX code. Signed-off-by: David Windsor [kees: adjust commit log, provide usage trace] Cc: Boaz Harrosh Signed-off-by: Kees Cook --- fs/exofs/super.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/exofs/super.c b/fs/exofs/super.c index 819624cfc8da..e5c532875bb7 100644 --- a/fs/exofs/super.c +++ b/fs/exofs/super.c @@ -192,10 +192,13 @@ static void exofs_init_once(void *foo) */ static int init_inodecache(void) { - exofs_inode_cachep = kmem_cache_create("exofs_inode_cache", + exofs_inode_cachep = kmem_cache_create_usercopy("exofs_inode_cache", sizeof(struct exofs_i_info), 0, SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD | - SLAB_ACCOUNT, exofs_init_once); + SLAB_ACCOUNT, + offsetof(struct exofs_i_info, i_data), + sizeof_field(struct exofs_i_info, i_data), + exofs_init_once); if (exofs_inode_cachep == NULL) return -ENOMEM; return 0;