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[89.148.117.163]) by smtp.gmail.com with ESMTPSA id w27-20020adf8bdb000000b00332e5624a31sm14745352wra.84.2023.11.28.08.03.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Nov 2023 08:03:49 -0800 (PST) From: Miklos Szeredi To: Christian Brauner Cc: linux-api@vger.kernel.org, linux-man@vger.kernel.org, linux-security-module@vger.kernel.org, Karel Zak , linux-fsdevel@vger.kernel.org, Ian Kent , David Howells , Al Viro Subject: [PATCH 4/4] listmount: allow continuing Date: Tue, 28 Nov 2023 17:03:35 +0100 Message-ID: <20231128160337.29094-5-mszeredi@redhat.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20231128160337.29094-1-mszeredi@redhat.com> References: <20231128160337.29094-1-mszeredi@redhat.com> Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Rename mnt_id_req.request_mask to .param to allow using it for listmount(2) as well. 1) If the buffer is full don't return EOVERFLOW, instead return the buffer size. This still allows detecting a full buffer. 2) listing is continued after the ID contained in .param. This allows listing the mount IDs in multiple listmount() invocations without having to resize buffer. If .param is zero, then the listing is started from the beginning, just like previously. Signed-off-by: Miklos Szeredi --- fs/namespace.c | 17 ++++++++--------- include/uapi/linux/mount.h | 9 ++++++++- 2 files changed, 16 insertions(+), 10 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 10cd651175b5..5c1455c4b53b 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -4942,7 +4942,7 @@ static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq, return -EFAULT; *ks = (struct kstatmount){ - .mask = kreq->request_mask, + .mask = kreq->param, .buf = buf, .bufsize = bufsize, .seq = { @@ -5020,14 +5020,11 @@ static ssize_t do_listmount(struct mount *first, struct path *orig, u64 mnt_id, if (err) return err; - for (ctr = 0, r = first; r; r = listmnt_next(r)) { + for (ctr = 0, r = first; r && ctr < bufsize; r = listmnt_next(r)) { if (r->mnt_id_unique == mnt_id) continue; if (!is_path_reachable(r, r->mnt.mnt_root, orig)) continue; - - if (ctr >= bufsize) - return -EOVERFLOW; ctr = array_index_nospec(ctr, bufsize); if (put_user(r->mnt_id_unique, buf + ctr)) return -EFAULT; @@ -5044,7 +5041,7 @@ SYSCALL_DEFINE4(listmount, const struct mnt_id_req __user *, req, struct mnt_id_req kreq; struct mount *first; struct path root, orig; - u64 mnt_id; + u64 mnt_id, last_mnt_id; ssize_t ret; if (flags) @@ -5052,9 +5049,8 @@ SYSCALL_DEFINE4(listmount, const struct mnt_id_req __user *, req, if (copy_from_user(&kreq, req, sizeof(kreq))) return -EFAULT; - if (kreq.request_mask != 0) - return -EINVAL; mnt_id = kreq.mnt_id; + last_mnt_id = kreq.param; down_read(&namespace_sem); get_fs_root(current->fs, &root); @@ -5067,7 +5063,10 @@ SYSCALL_DEFINE4(listmount, const struct mnt_id_req __user *, req, goto err; orig.dentry = orig.mnt->mnt_root; } - first = node_to_mount(rb_first(&ns->mounts)); + if (!last_mnt_id) + first = node_to_mount(rb_first(&ns->mounts)); + else + first = mnt_find_id_at(ns, last_mnt_id + 1); ret = do_listmount(first, &orig, mnt_id, buf, bufsize, &root); err: diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h index f6b35a15b7dd..dc9a0112d819 100644 --- a/include/uapi/linux/mount.h +++ b/include/uapi/linux/mount.h @@ -176,9 +176,16 @@ struct statmount { char str[]; /* Variable size part containing strings */ }; +/* + * Structure for passing mount ID and miscellaneous parameters to statmount(2) + * and listmount(2). + * + * For statmount(2) @param represents the request mask. + * For listmount(2) @param represents the last listed mount id (or zero). + */ struct mnt_id_req { __u64 mnt_id; - __u64 request_mask; + __u64 param; }; /* -- 2.41.0