Add syscall quotactl_path, a variant of quotactl which allows to specify
the mountpath instead of a path of to a block device.
The quotactl syscall expects a path to the mounted block device to
specify the filesystem to work on. This limits usage to filesystems
which actually have a block device. quotactl_path replaces the path
to the block device with a path where the filesystem is mounted at.
The global Q_SYNC command to sync all filesystems is not supported for
this new syscall, otherwise quotactl_path behaves like quotactl.
Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
---
fs/quota/quota.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 77 insertions(+)
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 6d16b2be5ac4..9ac09e128686 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -17,6 +17,7 @@
#include <linux/capability.h>
#include <linux/quotaops.h>
#include <linux/types.h>
+#include <linux/mount.h>
#include <linux/writeback.h>
#include <linux/nospec.h>
#include "compat.h"
@@ -968,3 +969,79 @@ SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
path_put(pathp);
return ret;
}
+
+SYSCALL_DEFINE4(quotactl_path, unsigned int, cmd, const char __user *,
+ mountpoint, qid_t, id, void __user *, addr)
+{
+ uint cmds, type;
+ struct super_block *sb = NULL;
+ struct path path, *pathp = NULL;
+ struct path mountpath;
+ bool excl = false, thawed = false;
+ int ret;
+
+ cmds = cmd >> SUBCMDSHIFT;
+ type = cmd & SUBCMDMASK;
+
+ if (type >= MAXQUOTAS)
+ return -EINVAL;
+
+ if (!mountpoint)
+ return -ENODEV;
+
+ /*
+ * Path for quotaon has to be resolved before grabbing superblock
+ * because that gets s_umount sem which is also possibly needed by path
+ * resolution (think about autofs) and thus deadlocks could arise.
+ */
+ if (cmds == Q_QUOTAON) {
+ ret = user_path_at(AT_FDCWD, addr,
+ LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT, &path);
+ if (ret)
+ pathp = ERR_PTR(ret);
+ else
+ pathp = &path;
+ }
+
+ ret = user_path_at(AT_FDCWD, mountpoint,
+ LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT, &mountpath);
+ if (ret)
+ goto out;
+
+ if (quotactl_cmd_onoff(cmds)) {
+ excl = true;
+ thawed = true;
+ } else if (quotactl_cmd_write(cmds)) {
+ thawed = true;
+ }
+
+ if (thawed) {
+ ret = mnt_want_write(mountpath.mnt);
+ if (ret)
+ goto out1;
+ }
+
+ sb = mountpath.dentry->d_inode->i_sb;
+
+ if (excl)
+ down_write(&sb->s_umount);
+ else
+ down_read(&sb->s_umount);
+
+ ret = do_quotactl(sb, type, cmds, id, addr, pathp);
+
+ if (excl)
+ up_write(&sb->s_umount);
+ else
+ up_read(&sb->s_umount);
+
+ if (thawed)
+ mnt_drop_write(mountpath.mnt);
+out1:
+ path_put(&mountpath);
+
+out:
+ if (pathp && !IS_ERR(pathp))
+ path_put(pathp);
+ return ret;
+}
--
2.20.1
