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authorChenXiaoSong <chenxiaosong2@huawei.com>2022-11-04 15:44:41 +0800
committerSteve French <stfrench@microsoft.com>2022-11-04 23:36:54 -0500
commit542228db2f28fdf775b301f2843e1fe486e7c797 (patch)
tree60ed90760ffef328e87d4da2c44a5b7ff2587e3c
parent23d9b9b757e8007204d8f71448ab55d5ef2ae8e5 (diff)
cifs: fix use-after-free on the link name
xfstests generic/011 reported use-after-free bug as follows: BUG: KASAN: use-after-free in __d_alloc+0x269/0x859 Read of size 15 at addr ffff8880078933a0 by task dirstress/952 CPU: 1 PID: 952 Comm: dirstress Not tainted 6.1.0-rc3+ #77 Call Trace: __dump_stack+0x23/0x29 dump_stack_lvl+0x51/0x73 print_address_description+0x67/0x27f print_report+0x3e/0x5c kasan_report+0x7b/0xa8 kasan_check_range+0x1b2/0x1c1 memcpy+0x22/0x5d __d_alloc+0x269/0x859 d_alloc+0x45/0x20c d_alloc_parallel+0xb2/0x8b2 lookup_open+0x3b8/0x9f9 open_last_lookups+0x63d/0xc26 path_openat+0x11a/0x261 do_filp_open+0xcc/0x168 do_sys_openat2+0x13b/0x3f7 do_sys_open+0x10f/0x146 __se_sys_creat+0x27/0x2e __x64_sys_creat+0x55/0x6a do_syscall_64+0x40/0x96 entry_SYSCALL_64_after_hwframe+0x63/0xcd Allocated by task 952: kasan_save_stack+0x1f/0x42 kasan_set_track+0x21/0x2a kasan_save_alloc_info+0x17/0x1d __kasan_kmalloc+0x7e/0x87 __kmalloc_node_track_caller+0x59/0x155 kstrndup+0x60/0xe6 parse_mf_symlink+0x215/0x30b check_mf_symlink+0x260/0x36a cifs_get_inode_info+0x14e1/0x1690 cifs_revalidate_dentry_attr+0x70d/0x964 cifs_revalidate_dentry+0x36/0x62 cifs_d_revalidate+0x162/0x446 lookup_open+0x36f/0x9f9 open_last_lookups+0x63d/0xc26 path_openat+0x11a/0x261 do_filp_open+0xcc/0x168 do_sys_openat2+0x13b/0x3f7 do_sys_open+0x10f/0x146 __se_sys_creat+0x27/0x2e __x64_sys_creat+0x55/0x6a do_syscall_64+0x40/0x96 entry_SYSCALL_64_after_hwframe+0x63/0xcd Freed by task 950: kasan_save_stack+0x1f/0x42 kasan_set_track+0x21/0x2a kasan_save_free_info+0x1c/0x34 ____kasan_slab_free+0x1c1/0x1d5 __kasan_slab_free+0xe/0x13 __kmem_cache_free+0x29a/0x387 kfree+0xd3/0x10e cifs_fattr_to_inode+0xb6a/0xc8c cifs_get_inode_info+0x3cb/0x1690 cifs_revalidate_dentry_attr+0x70d/0x964 cifs_revalidate_dentry+0x36/0x62 cifs_d_revalidate+0x162/0x446 lookup_open+0x36f/0x9f9 open_last_lookups+0x63d/0xc26 path_openat+0x11a/0x261 do_filp_open+0xcc/0x168 do_sys_openat2+0x13b/0x3f7 do_sys_open+0x10f/0x146 __se_sys_creat+0x27/0x2e __x64_sys_creat+0x55/0x6a do_syscall_64+0x40/0x96 entry_SYSCALL_64_after_hwframe+0x63/0xcd When opened a symlink, link name is from 'inode->i_link', but it may be reset to a new value when revalidate the dentry. If some processes get the link name on the race scenario, then UAF will happen on link name. Fix this by implementing 'get_link' interface to duplicate the link name. Fixes: 76894f3e2f71 ("cifs: improve symlink handling for smb2+") Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com> Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz> Signed-off-by: Steve French <stfrench@microsoft.com>
-rw-r--r--fs/cifs/cifsfs.c26
-rw-r--r--fs/cifs/inode.c5
2 files changed, 25 insertions, 6 deletions
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index d0b9fec111aa..fe220686bba4 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1143,8 +1143,32 @@ const struct inode_operations cifs_file_inode_ops = {
.fiemap = cifs_fiemap,
};
+const char *cifs_get_link(struct dentry *dentry, struct inode *inode,
+ struct delayed_call *done)
+{
+ char *target_path;
+
+ target_path = kmalloc(PATH_MAX, GFP_KERNEL);
+ if (!target_path)
+ return ERR_PTR(-ENOMEM);
+
+ spin_lock(&inode->i_lock);
+ if (likely(CIFS_I(inode)->symlink_target)) {
+ strscpy(target_path, CIFS_I(inode)->symlink_target, PATH_MAX);
+ } else {
+ kfree(target_path);
+ target_path = ERR_PTR(-EOPNOTSUPP);
+ }
+ spin_unlock(&inode->i_lock);
+
+ if (!IS_ERR(target_path))
+ set_delayed_call(done, kfree_link, target_path);
+
+ return target_path;
+}
+
const struct inode_operations cifs_symlink_inode_ops = {
- .get_link = simple_get_link,
+ .get_link = cifs_get_link,
.permission = cifs_permission,
.listxattr = cifs_listxattr,
};
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 9bde08d44617..4e2ca3c6e5c0 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -215,11 +215,6 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
kfree(cifs_i->symlink_target);
cifs_i->symlink_target = fattr->cf_symlink_target;
fattr->cf_symlink_target = NULL;
-
- if (unlikely(!cifs_i->symlink_target))
- inode->i_link = ERR_PTR(-EOPNOTSUPP);
- else
- inode->i_link = cifs_i->symlink_target;
}
spin_unlock(&inode->i_lock);