SymbX/systemd
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

fd-util: skip to check mount ID if kernel is too old and /proc is not mounted

Browse Source 
Now, dir_fd_is_root() is heavily used in chaseat(), which is used at
various places. If the kernel is too old and /proc is not mounted, then
there is no way to get the mount ID of a directory. In that case, let's
silently skip the mount ID check.

Fixes https://github.com/systemd/systemd/pull/27299#issuecomment-1511403680.
This commit is contained in:
Yu Watanabe
2023-04-19 03:38:47 +09:00
parent 4b1e461c49
commit 8d3c49b168
1 changed files with 15 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/basic/fd-util.c
+15 -7
View File
@@ -911,10 +911,23 @@ int dir_fd_is_root(int dir_fd) {
if (!statx_inode_same(&st.sx, &pst.sx))
return false;
/* Even if the parent directory has the same inode, the fd may not point to the root directory "/",
* and we also need to check that the mount ids are the same. Otherwise, a construct like the
* following could be used to trick us:
*
* $ mkdir /tmp/x /tmp/x/y
* $ mount --bind /tmp/x /tmp/x/y
*
* Note, statx() does not provide the mount ID and path_get_mnt_id_at() does not work when an old
* kernel is used without /proc mounted. In that case, let's assume that we do not have such spurious
* mount points in an early boot stage, and silently skip the following check. */
if (!FLAGS_SET(st.nsx.stx_mask, STATX_MNT_ID)) {
int mntid;
r = path_get_mnt_id_at(dir_fd, "", &mntid);
if (r == -ENOSYS)
return true; /* skip the mount ID check */
if (r < 0)
return r;
assert(mntid >= 0);
@@ -927,6 +940,8 @@ int dir_fd_is_root(int dir_fd) {
int mntid;
r = path_get_mnt_id_at(dir_fd, "..", &mntid);
if (r == -ENOSYS)
return true; /* skip the mount ID check */
if (r < 0)
return r;
assert(mntid >= 0);
@@ -935,13 +950,6 @@ int dir_fd_is_root(int dir_fd) {
pst.nsx.stx_mask |= STATX_MNT_ID;
}
/* Even if the parent directory has the same inode, the fd may not point to the root directory "/",
* and we also need to check that the mount ids are the same. Otherwise, a construct like the
* following could be used to trick us:
*
* $ mkdir /tmp/x /tmp/x/y
* $ mount --bind /tmp/x /tmp/x/y
*/
return statx_mount_same(&st.nsx, &pst.nsx);
}