[PATCH v1 05/14] mm/mshare: Add locking to msharefs syscalls

Khalid Aziz
2022-04-11T16:08:11Z

Lock the root inode for msharefs when creating a new file or
deleting an existing one to avoid races. mshare syscalls are low
frequency operations, so locking the root inode is reasonable.

Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
---
mm/mshare.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/mm/mshare.c b/mm/mshare.c
index b9d7836f9bd1..85ccb7f02f33 100644
--- a/mm/mshare.c
+++ b/mm/mshare.c
@@ -195,11 +195,12 @@ SYSCALL_DEFINE5(mshare, const char __user *, name, unsigned long, addr,
err = msharefs_d_hash(msharefs_sb->s_root, &namestr);
if (err)
goto err_out;
+ inode_lock(d_inode(msharefs_sb->s_root));
dentry = d_lookup(msharefs_sb->s_root, &namestr);
if (dentry && (oflag & (O_EXCL|O_CREAT))) {
err = -EEXIST;
dput(dentry);
- goto err_out;
+ goto err_unlock_inode;
}

if (dentry) {
@@ -232,6 +233,7 @@ SYSCALL_DEFINE5(mshare, const char __user *, name, unsigned long, addr,
goto err_relinfo;
}

+ inode_unlock(d_inode(msharefs_sb->s_root));
putname(fname);
return 0;

@@ -239,6 +241,8 @@ SYSCALL_DEFINE5(mshare, const char __user *, name, unsigned long, addr,
kfree(info);
err_relmm:
mmput(mm);
+err_unlock_inode:
+ inode_unlock(d_inode(msharefs_sb->s_root));
err_out:
putname(fname);
return err;
@@ -264,10 +268,11 @@ SYSCALL_DEFINE1(mshare_unlink, const char *, name)
err = msharefs_d_hash(msharefs_sb->s_root, &namestr);
if (err)
goto err_out;
+ inode_lock(d_inode(msharefs_sb->s_root));
dentry = d_lookup(msharefs_sb->s_root, &namestr);
if (dentry == NULL) {
err = -EINVAL;
- goto err_out;
+ goto err_unlock_inode;
}

inode = d_inode(dentry);
@@ -290,11 +295,14 @@ SYSCALL_DEFINE1(mshare_unlink, const char *, name)
dput(dentry);
}

+ inode_unlock(d_inode(msharefs_sb->s_root));
putname(fname);
return 0;

err_dput:
dput(dentry);
+err_unlock_inode:
+ inode_unlock(d_inode(msharefs_sb->s_root));
err_out:
putname(fname);
return err;
--
2.32.0