From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> To: Al Viro <viro@zeniv.linux.org.uk> Cc: Eric Biggers <ebiggers3@gmail.com>, Dmitry Vyukov <dvyukov@google.com>, Kees Cook <keescook@chromium.org>, Andrew Morton <akpm@linux-foundation.org>, "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>, Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, syzbot <syzbot+e93a80c1bb7c5c56e522461c149f8bf55eab1b2b@syzkaller.appspotmail.com> Subject: [PATCH v2 (resend)] fs: Allow opening only regular files during execve(). Date: Fri, 8 Mar 2019 20:20:17 +0900 Message-ID: <1552044017-7890-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> (raw) syzbot is hitting lockdep warning [1] due to trying to open a fifo during an execve() operation. But we don't need to open non regular files during an execve() operation, for all files which we will need are the executable file itself and the interpreter programs like /bin/sh and ld-linux.so.2 . Since the manpage for execve(2) says that execve() returns EACCES when the file or a script interpreter is not a regular file, and the manpage for uselib(2) says that uselib() can return EACCES, and we use FMODE_EXEC when opening for execve()/uselib(), we can bail out if a non regular file is requested with FMODE_EXEC set. Since this deadlock followed by khungtaskd warnings is trivially reproducible by a local unprivileged user, and syzbot's frequent crash due to this deadlock defers finding other bugs, let's workaround this deadlock until we get a chance to find a better solution. [1] https://syzkaller.appspot.com/bug?id=b5095bfec44ec84213bac54742a82483aad578ce Reported-by: syzbot <syzbot+e93a80c1bb7c5c56e522461c149f8bf55eab1b2b@syzkaller.appspotmail.com> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Fixes: 8924feff66f35fe2 ("splice: lift pipe_lock out of splice_to_pipe()") Cc: <stable@vger.kernel.org> # 4.9+ --- fs/open.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/open.c b/fs/open.c index 0285ce7..f1c2f85 100644 --- a/fs/open.c +++ b/fs/open.c @@ -733,6 +733,12 @@ static int do_dentry_open(struct file *f, return 0; } + /* Any file opened for execve()/uselib() has to be a regular file. */ + if (unlikely(f->f_flags & FMODE_EXEC && !S_ISREG(inode->i_mode))) { + error = -EACCES; + goto cleanup_file; + } + if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) { error = get_write_access(inode); if (unlikely(error)) -- 1.8.3.1
next reply index Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-03-08 11:20 Tetsuo Handa [this message] 2019-03-08 15:45 ` Kees Cook
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=1552044017-7890-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp \ --to=penguin-kernel@i-love.sakura.ne.jp \ --cc=akpm@linux-foundation.org \ --cc=dvyukov@google.com \ --cc=ebiggers3@gmail.com \ --cc=keescook@chromium.org \ --cc=linux-fsdevel@vger.kernel.org \ --cc=syzbot+e93a80c1bb7c5c56e522461c149f8bf55eab1b2b@syzkaller.appspotmail.com \ --cc=viro@zeniv.linux.org.uk \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
Linux-Fsdevel Archive on lore.kernel.org Archives are clonable: git clone --mirror https://lore.kernel.org/linux-fsdevel/0 linux-fsdevel/git/0.git # If you have public-inbox 1.1+ installed, you may # initialize and index your mirror using the following commands: public-inbox-init -V2 linux-fsdevel linux-fsdevel/ https://lore.kernel.org/linux-fsdevel \ linux-fsdevel@vger.kernel.org public-inbox-index linux-fsdevel Example config snippet for mirrors Newsgroup available over NNTP: nntp://nntp.lore.kernel.org/org.kernel.vger.linux-fsdevel AGPL code for this site: git clone https://public-inbox.org/public-inbox.git