From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aleksa Sarai Subject: [PATCH v13 2/9] procfs: switch magic-link modes to be more sane Date: Tue, 1 Oct 2019 04:33:09 +1000 Message-ID: <20190930183316.10190-3-cyphar@cyphar.com> References: <20190930183316.10190-1-cyphar@cyphar.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=jB7cSV3HV6OWM8RRPFqeAhW3VWxpTWaD21A2dYo48Nc=; b=Y8vpewDG8ePLsF rBQHr3JXXBlxnYSfyW0N/4QZmxrMtzIFg1op/f/MU73MxOGFknNnpNZMUHPIA1s6MBHkYJ9LwA8U3 fgz6T4PZyBJvupx3p1FwzSTh8f5QCbQJLd3aZ1h7MRHaFXB2j3sKHs2mKXAOlb8X+iW2Uuv/aLmWG yYC1aF25OO0TWkbrZoLa3ezCU9NpjjbxrAdaq9AXiAE9/I+II2e8L+qTQwI5uxw/IxWnQoRjD2mgV B/ZbLco+MUmI/wc+PqCoo5pqEDjsyaYnZ/shI37Bvy4CGpYS6N+rY9rV451m1AGKpt5E8Us2D52kM SG8QqalsH2Vrzf0x8lxw==; In-Reply-To: <20190930183316.10190-1-cyphar@cyphar.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Al Viro , Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Ingo Molnar , Peter Zijlstra Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Alexander Shishkin , Rasmus Villemoes , Alexei Starovoitov , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, Jiri Olsa , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Tycho Andersen , Aleksa Sarai , linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn , linuxppc-dev@lists.ozlabs.org, Aleksa Sarai , Andy Lutomirski , Namhyung Kim , David Drysdale , Christian Brauner , libc-alpha@sourceware.org, linux-parisc@vger.kernel.org, linux-m68k@li Now that magic-link modes are obeyed for file re-opening purposes, some of the pre-existing magic-link modes need to be adjusted to be more semantically correct. The most blatant example of this is /proc/self/exe, which had a mode of a+rwx even though tautologically the file could never be opened for writing (because it is the current->mm of a live process). With the new O_PATH restrictions, changing the default mode of these magic-links allows us to avoid delayed-access attacks such as we saw in CVE-2019-5736. Signed-off-by: Aleksa Sarai --- fs/proc/base.c | 20 ++++++++++---------- fs/proc/namespaces.c | 2 +- 2 files changed, 11 insertions(+), 11 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 96c9ec66846f..908edd0e875e 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -133,9 +133,9 @@ struct pid_entry { #define DIR(NAME, MODE, iops, fops) \ NOD(NAME, (S_IFDIR|(MODE)), &iops, &fops, {} ) -#define LNK(NAME, get_link) \ - NOD(NAME, (S_IFLNK|S_IRWXUGO), \ - &proc_pid_link_inode_operations, NULL, \ +#define LNK(NAME, MODE, get_link) \ + NOD(NAME, (S_IFLNK|(MODE)), \ + &proc_pid_link_inode_operations, NULL, \ { .proc_get_link = get_link } ) #define REG(NAME, MODE, fops) \ NOD(NAME, (S_IFREG|(MODE)), NULL, &fops, {}) @@ -3047,9 +3047,9 @@ static const struct pid_entry tgid_base_stuff[] = { REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations), #endif REG("mem", S_IRUSR|S_IWUSR, proc_mem_operations), - LNK("cwd", proc_cwd_link), - LNK("root", proc_root_link), - LNK("exe", proc_exe_link), + LNK("cwd", S_IRWXUGO, proc_cwd_link), + LNK("root", S_IRWXUGO, proc_root_link), + LNK("exe", S_IRUGO|S_IXUGO, proc_exe_link), REG("mounts", S_IRUGO, proc_mounts_operations), REG("mountinfo", S_IRUGO, proc_mountinfo_operations), REG("mountstats", S_IRUSR, proc_mountstats_operations), @@ -3448,11 +3448,11 @@ static const struct pid_entry tid_base_stuff[] = { REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations), #endif REG("mem", S_IRUSR|S_IWUSR, proc_mem_operations), - LNK("cwd", proc_cwd_link), - LNK("root", proc_root_link), - LNK("exe", proc_exe_link), + LNK("cwd", S_IRWXUGO, proc_cwd_link), + LNK("root", S_IRWXUGO, proc_root_link), + LNK("exe", S_IRUGO|S_IXUGO, proc_exe_link), REG("mounts", S_IRUGO, proc_mounts_operations), - REG("mountinfo", S_IRUGO, proc_mountinfo_operations), + REG("mountinfo", S_IRUGO, proc_mountinfo_operations), #ifdef CONFIG_PROC_PAGE_MONITOR REG("clear_refs", S_IWUSR, proc_clear_refs_operations), REG("smaps", S_IRUGO, proc_pid_smaps_operations), diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c index 0142992eceea..cadf0ae796a2 100644 --- a/fs/proc/namespaces.c +++ b/fs/proc/namespaces.c @@ -94,7 +94,7 @@ static struct dentry *proc_ns_instantiate(struct dentry *dentry, struct inode *inode; struct proc_inode *ei; - inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK | S_IRWXUGO); + inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK | S_IRUGO); if (!inode) return ERR_PTR(-ENOENT); -- 2.23.0