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ubifs: Fix races between xattr_{set|get} and listxattr operations

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UBIFS may occur some problems with concurrent xattr_{set|get} and
listxattr operations, such as assertion failure, memory corruption,
stale xattr value[1].

Fix it by importing a new rw-lock in @ubifs_inode to serilize write
operations on xattr, concurrent read operations are still effective,
just like ext4.

[1] https://lore.kernel.org/linux-mtd/20200630130438.141649-1-houtao1@huawei.com

Fixes: 1e51764a3c ("UBIFS: add new flash file system")
Cc: stable@vger.kernel.org  # v2.6+
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Zhihao Cheng 2021-05-31 20:52:09 +08:00 committed by Richard Weinberger
parent be076fdf83
commit f4e3634a3b
3 changed files with 36 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
fs/ubifs/super.c
View File

@ -275,6 +275,7 @@ static struct inode *ubifs_alloc_inode(struct super_block *sb)
memset((void *)ui + sizeof(struct inode), 0,
sizeof(struct ubifs_inode) - sizeof(struct inode));
mutex_init(&ui->ui_mutex);
init_rwsem(&ui->xattr_sem);
spin_lock_init(&ui->ui_lock);
return &ui->vfs_inode;
};

2
fs/ubifs/ubifs.h
View File

@ -356,6 +356,7 @@ struct ubifs_gced_idx_leb {
* @ui_mutex: serializes inode write-back with the rest of VFS operations,
* serializes "clean <-> dirty" state changes, serializes bulk-read,
* protects @dirty, @bulk_read, @ui_size, and @xattr_size
* @xattr_sem: serilizes write operations (remove|set|create) on xattr
* @ui_lock: protects @synced_i_size
* @synced_i_size: synchronized size of inode, i.e. the value of inode size
* currently stored on the flash; used only for regular file
@ -409,6 +410,7 @@ struct ubifs_inode {
unsigned int bulk_read:1;
unsigned int compr_type:2;
struct mutex ui_mutex;
struct rw_semaphore xattr_sem;
spinlock_t ui_lock;
loff_t synced_i_size;
loff_t ui_size;

44
fs/ubifs/xattr.c
View File

@ -285,6 +285,7 @@ int ubifs_xattr_set(struct inode *host, const char *name, const void *value,
if (!xent)
return -ENOMEM;
down_write(&ubifs_inode(host)->xattr_sem);
/*
* The extended attribute entries are stored in LNC, so multiple
* look-ups do not involve reading the flash.
@ -319,6 +320,7 @@ int ubifs_xattr_set(struct inode *host, const char *name, const void *value,
iput(inode);
out_free:
up_write(&ubifs_inode(host)->xattr_sem);
kfree(xent);
return err;
}
@ -341,18 +343,19 @@ ssize_t ubifs_xattr_get(struct inode *host, const char *name, void *buf,
if (!xent)
return -ENOMEM;
down_read(&ubifs_inode(host)->xattr_sem);
xent_key_init(c, &key, host->i_ino, &nm);
err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
if (err) {
if (err == -ENOENT)
err = -ENODATA;
goto out_unlock;
goto out_cleanup;
}
inode = iget_xattr(c, le64_to_cpu(xent->inum));
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
goto out_unlock;
goto out_cleanup;
}
ui = ubifs_inode(inode);
@ -374,7 +377,8 @@ ssize_t ubifs_xattr_get(struct inode *host, const char *name, void *buf,
out_iput:
mutex_unlock(&ui->ui_mutex);
iput(inode);
out_unlock:
out_cleanup:
up_read(&ubifs_inode(host)->xattr_sem);
kfree(xent);
return err;
}
@ -406,16 +410,21 @@ ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino,
dentry, size);
down_read(&host_ui->xattr_sem);
len = host_ui->xattr_names + host_ui->xattr_cnt;
if (!buffer)
if (!buffer) {
/*
* We should return the minimum buffer size which will fit a
* null-terminated list of all the extended attribute names.
*/
return len;
err = len;
goto out_err;
}
if (len > size)
return -ERANGE;
if (len > size) {
err = -ERANGE;
goto out_err;
}
lowest_xent_key(c, &key, host->i_ino);
while (1) {
@ -437,8 +446,9 @@ ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
pxent = xent;
key_read(c, &xent->key, &key);
}
kfree(pxent);
up_read(&host_ui->xattr_sem);
if (err != -ENOENT) {
ubifs_err(c, "cannot find next direntry, error %d", err);
return err;
@ -446,6 +456,10 @@ ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
ubifs_assert(c, written <= size);
return written;
out_err:
up_read(&host_ui->xattr_sem);
return err;
}
static int remove_xattr(struct ubifs_info *c, struct inode *host,
@ -504,6 +518,7 @@ int ubifs_purge_xattrs(struct inode *host)
ubifs_warn(c, "inode %lu has too many xattrs, doing a non-atomic deletion",
host->i_ino);
down_write(&ubifs_inode(host)->xattr_sem);
lowest_xent_key(c, &key, host->i_ino);
while (1) {
xent = ubifs_tnc_next_ent(c, &key, &nm);
@ -523,7 +538,7 @@ int ubifs_purge_xattrs(struct inode *host)
ubifs_ro_mode(c, err);
kfree(pxent);
kfree(xent);
return err;
goto out_err;
}
ubifs_assert(c, ubifs_inode(xino)->xattr);
@ -535,7 +550,7 @@ int ubifs_purge_xattrs(struct inode *host)
kfree(xent);
iput(xino);
ubifs_err(c, "cannot remove xattr, error %d", err);
return err;
goto out_err;
}
iput(xino);
@ -544,14 +559,19 @@ int ubifs_purge_xattrs(struct inode *host)
pxent = xent;
key_read(c, &xent->key, &key);
}
kfree(pxent);
up_write(&ubifs_inode(host)->xattr_sem);
if (err != -ENOENT) {
ubifs_err(c, "cannot find next direntry, error %d", err);
return err;
}
return 0;
out_err:
up_write(&ubifs_inode(host)->xattr_sem);
return err;
}
/**
@ -594,6 +614,7 @@ static int ubifs_xattr_remove(struct inode *host, const char *name)
if (!xent)
return -ENOMEM;
down_write(&ubifs_inode(host)->xattr_sem);
xent_key_init(c, &key, host->i_ino, &nm);
err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
if (err) {
@ -618,6 +639,7 @@ static int ubifs_xattr_remove(struct inode *host, const char *name)
iput(inode);
out_free:
up_write(&ubifs_inode(host)->xattr_sem);
kfree(xent);
return err;
}