On Thu, Jun 17, 2021 at 04:15:18PM +0200, Greg Kurz wrote: > 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 <gr...@kaod.org> > --- > tools/virtiofsd/passthrough_ll.c | 6 ++++++ > 1 file changed, 6 insertions(+)
Thank you! Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
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