From: Jann Horn To: security@kernel.org Cc: Jann Horn Subject: [PATCH 2/3] ecryptfs: forbid opening files without mmap handler Date: Wed, 1 Jun 2016 11:55:06 +0200 Message-Id: <1464774907-7753-2-git-send-email-jannh@google.com> X-Mailer: git-send-email 2.8.0.rc3.226.g39d4020 In-Reply-To: <1464774907-7753-1-git-send-email-jannh@google.com> References: <1464774907-7753-1-git-send-email-jannh@google.com> X-Spam-Status: No, hits=-5.1 required=5 tests=DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VERIFIED X-Spam-Checker-Version: SpamAssassin 3.4.0-outflux_revision__1.66__ X-Virus-Scanned: ClamAV using ClamSMTP Envelope-To: kees@outflux.net X-MIMEDefang-Filter: outflux$Revision: 1.316 $ X-HELO: www.outflux.net X-Scanned-By: MIMEDefang 2.73 This prevents users from triggering an exploitable stack overflow through a recursive invocation of pagefault handling that involves mapping procfs files into virtual memory. Signed-off-by: Jann Horn Cc: stable@vger.kernel.org --- fs/ecryptfs/kthread.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/ecryptfs/kthread.c b/fs/ecryptfs/kthread.c index 866bb18..e818f5a 100644 --- a/fs/ecryptfs/kthread.c +++ b/fs/ecryptfs/kthread.c @@ -25,6 +25,7 @@ #include #include #include +#include #include "ecryptfs_kernel.h" struct ecryptfs_open_req { @@ -147,7 +148,7 @@ int ecryptfs_privileged_open(struct file **lower_file, flags |= IS_RDONLY(d_inode(lower_dentry)) ? O_RDONLY : O_RDWR; (*lower_file) = dentry_open(&req.path, flags, cred); if (!IS_ERR(*lower_file)) - goto out; + goto have_file; if ((flags & O_ACCMODE) == O_RDONLY) { rc = PTR_ERR((*lower_file)); goto out; @@ -165,8 +166,16 @@ int ecryptfs_privileged_open(struct file **lower_file, mutex_unlock(&ecryptfs_kthread_ctl.mux); wake_up(&ecryptfs_kthread_ctl.wait); wait_for_completion(&req.done); - if (IS_ERR(*lower_file)) + if (IS_ERR(*lower_file)) { rc = PTR_ERR(*lower_file); + goto out; + } +have_file: + if ((*lower_file)->f_op->mmap == NULL) { + fput(*lower_file); + *lower_file = NULL; + rc = -EMEDIUMTYPE; + } out: return rc; } -- 2.8.0.rc3.226.g39d4020