From: Greg Kurz <groug@kaod.org> To: qemu-devel@nongnu.org Cc: Miklos Szeredi <miklos@szeredi.hu>, Greg Kurz <groug@kaod.org>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, virtio-fs@redhat.com, Stefan Hajnoczi <stefanha@redhat.com>, Vivek Goyal <vgoyal@redhat.com> Subject: [PATCH] virtiofsd: Don't allow file creation with FUSE_OPEN Date: Thu, 17 Jun 2021 16:15:18 +0200 [thread overview] Message-ID: <20210617141518.304659-1-groug@kaod.org> (raw) A well behaved FUSE client uses FUSE_CREATE to create files. It isn't supposed to pass O_CREAT along a FUSE_OPEN request, as documented in the "fuse_lowlevel.h" header : /** * Open a file * * Open flags are available in fi->flags. The following rules * apply. * * - Creation (O_CREAT, O_EXCL, O_NOCTTY) flags will be * filtered out / handled by the kernel. But if it does anyway, virtiofsd crashes with: *** invalid openat64 call: O_CREAT or O_TMPFILE without mode ***: terminated This is because virtiofsd ends up passing this flag to openat() without passing a mode_t 4th argument which is mandatory with O_CREAT, and glibc aborts. The offending path is: lo_open() lo_do_open() lo_inode_open() Other callers of lo_inode_open() only pass O_RDWR and lo_create() passes a valid fd to lo_do_open() which thus doesn't even call lo_inode_open() in this case. Specifying O_CREAT with FUSE_OPEN is a protocol violation. Check this in lo_open() and return an error to the client : EINVAL since this is already what glibc returns with other illegal flag combinations. The FUSE filesystem doesn't currently support O_TMPFILE, but the very same would happen if O_TMPFILE was passed in a FUSE_OPEN request. Check that as well. Signed-off-by: Greg Kurz <groug@kaod.org> --- tools/virtiofsd/passthrough_ll.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index 49c21fd85570..14f62133131c 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -2145,6 +2145,12 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) return; } + /* File creation is handled by lo_create() */ + if (fi->flags & (O_CREAT | O_TMPFILE)) { + fuse_reply_err(req, EINVAL); + return; + } + err = lo_do_open(lo, inode, -1, fi); lo_inode_put(lo, &inode); if (err) { -- 2.31.1
WARNING: multiple messages have this Message-ID (diff)
From: Greg Kurz <groug@kaod.org> To: qemu-devel@nongnu.org Cc: Miklos Szeredi <miklos@szeredi.hu>, virtio-fs@redhat.com, Vivek Goyal <vgoyal@redhat.com> Subject: [Virtio-fs] [PATCH] virtiofsd: Don't allow file creation with FUSE_OPEN Date: Thu, 17 Jun 2021 16:15:18 +0200 [thread overview] Message-ID: <20210617141518.304659-1-groug@kaod.org> (raw) A well behaved FUSE client uses FUSE_CREATE to create files. It isn't supposed to pass O_CREAT along a FUSE_OPEN request, as documented in the "fuse_lowlevel.h" header : /** * Open a file * * Open flags are available in fi->flags. The following rules * apply. * * - Creation (O_CREAT, O_EXCL, O_NOCTTY) flags will be * filtered out / handled by the kernel. But if it does anyway, virtiofsd crashes with: *** invalid openat64 call: O_CREAT or O_TMPFILE without mode ***: terminated This is because virtiofsd ends up passing this flag to openat() without passing a mode_t 4th argument which is mandatory with O_CREAT, and glibc aborts. The offending path is: lo_open() lo_do_open() lo_inode_open() Other callers of lo_inode_open() only pass O_RDWR and lo_create() passes a valid fd to lo_do_open() which thus doesn't even call lo_inode_open() in this case. Specifying O_CREAT with FUSE_OPEN is a protocol violation. Check this in lo_open() and return an error to the client : EINVAL since this is already what glibc returns with other illegal flag combinations. The FUSE filesystem doesn't currently support O_TMPFILE, but the very same would happen if O_TMPFILE was passed in a FUSE_OPEN request. Check that as well. Signed-off-by: Greg Kurz <groug@kaod.org> --- tools/virtiofsd/passthrough_ll.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index 49c21fd85570..14f62133131c 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -2145,6 +2145,12 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) return; } + /* File creation is handled by lo_create() */ + if (fi->flags & (O_CREAT | O_TMPFILE)) { + fuse_reply_err(req, EINVAL); + return; + } + err = lo_do_open(lo, inode, -1, fi); lo_inode_put(lo, &inode); if (err) { -- 2.31.1
next reply other threads:[~2021-06-17 14:18 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-17 14:15 Greg Kurz [this message] 2021-06-17 14:15 ` [Virtio-fs] [PATCH] virtiofsd: Don't allow file creation with FUSE_OPEN Greg Kurz 2021-06-17 14:29 ` Dr. David Alan Gilbert 2021-06-17 14:29 ` [Virtio-fs] " Dr. David Alan Gilbert 2021-06-17 16:18 ` Greg Kurz 2021-06-17 16:18 ` [Virtio-fs] " Greg Kurz 2021-06-18 1:40 ` Vivek Goyal 2021-06-18 1:40 ` [Virtio-fs] " Vivek Goyal 2021-06-18 8:20 ` Greg Kurz 2021-06-18 8:20 ` [Virtio-fs] " Greg Kurz 2021-06-18 8:58 ` Miklos Szeredi 2021-06-18 8:58 ` [Virtio-fs] " Miklos Szeredi 2021-06-18 9:21 ` Greg Kurz 2021-06-18 9:21 ` [Virtio-fs] " Greg Kurz 2021-06-18 9:34 ` Miklos Szeredi 2021-06-18 9:34 ` [Virtio-fs] " Miklos Szeredi 2021-06-21 13:36 ` Stefan Hajnoczi 2021-06-21 13:36 ` [Virtio-fs] " Stefan Hajnoczi 2021-06-22 16:01 ` Greg Kurz 2021-06-22 16:01 ` [Virtio-fs] " Greg Kurz
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