Date: Wed, 22 Mar 2023 13:19:35 GMT From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 0f5b6f9a041e - main - fdescfs: Fix a file ref leak Message-ID: <202303221319.32MDJZ7T097041@gitrepo.freebsd.org>
next in thread | raw e-mail | index | archive | help
The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=0f5b6f9a041e9cca3b376f6ec909374938887a3b commit 0f5b6f9a041e9cca3b376f6ec909374938887a3b Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2023-03-22 12:52:57 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2023-03-22 13:19:27 +0000 fdescfs: Fix a file ref leak In fdesc_lookup(), vn_vget_ino_gen() may fail without invoking the callback, in which case the ref on fp is leaked. This happens if the fdescfs mount is being concurrently unmounted. Moreover, we cannot safely drop the ref while the dvp is locked. So: - Use a flag variable to indicate whether the ref is dropped. - Reorganize things to handle the leak. Reported by: C Turt <ecturt@gmail.com> Reviewed by: mjg, kib Tested by: pho MFC after: 2 weeks Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D39189 --- sys/fs/fdescfs/fdesc_vnops.c | 42 +++++++++++++++++++++++++----------------- 1 file changed, 25 insertions(+), 17 deletions(-) diff --git a/sys/fs/fdescfs/fdesc_vnops.c b/sys/fs/fdescfs/fdesc_vnops.c index 0949dcc7eb29..d3c7951672cf 100644 --- a/sys/fs/fdescfs/fdesc_vnops.c +++ b/sys/fs/fdescfs/fdesc_vnops.c @@ -246,6 +246,7 @@ struct fdesc_get_ino_args { int ix; struct file *fp; struct thread *td; + bool fdropped; }; static int @@ -268,6 +269,7 @@ fdesc_get_ino_alloc(struct mount *mp, void *arg, int lkflags, error = fdesc_allocvp(a->ftype, a->fd_fd, a->ix, mp, rvp); } fdrop(a->fp, a->td); + a->fdropped = true; return (error); } @@ -288,6 +290,7 @@ fdesc_lookup(struct vop_lookup_args *ap) int nlen = cnp->cn_namelen; u_int fd, fd1; int error; + bool fdropped; struct vnode *fvp; if ((cnp->cn_flags & ISLASTCN) && @@ -331,24 +334,10 @@ fdesc_lookup(struct vop_lookup_args *ap) */ if ((error = fget(td, fd, &cap_no_rights, &fp)) != 0) goto bad; + fdropped = false; - /* Check if we're looking up ourselves. */ - if (VTOFDESC(dvp)->fd_ix == FD_DESC + fd) { - /* - * In case we're holding the last reference to the file, the dvp - * will be re-acquired. - */ - vhold(dvp); - VOP_UNLOCK(dvp); - fdrop(fp, td); - - /* Re-aquire the lock afterwards. */ - vn_lock(dvp, LK_RETRY | LK_EXCLUSIVE); - vdrop(dvp); - fvp = dvp; - if (VN_IS_DOOMED(dvp)) - error = ENOENT; - } else { + /* Make sure we're not looking up the dvp itself. */ + if (VTOFDESC(dvp)->fd_ix != FD_DESC + fd) { /* * Unlock our root node (dvp) when doing this, since we might * deadlock since the vnode might be locked by another thread @@ -362,8 +351,27 @@ fdesc_lookup(struct vop_lookup_args *ap) arg.ix = FD_DESC + fd; arg.fp = fp; arg.td = td; + arg.fdropped = fdropped; error = vn_vget_ino_gen(dvp, fdesc_get_ino_alloc, &arg, LK_EXCLUSIVE, &fvp); + fdropped = arg.fdropped; + } + + if (!fdropped) { + /* + * In case we're holding the last reference to the file, the dvp + * will be re-acquired. + */ + vhold(dvp); + VOP_UNLOCK(dvp); + fdrop(fp, td); + fdropped = true; + + vn_lock(dvp, LK_RETRY | LK_EXCLUSIVE); + vdrop(dvp); + fvp = dvp; + if (error == 0 && VN_IS_DOOMED(dvp)) + error = ENOENT; } if (error)
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?202303221319.32MDJZ7T097041>