| Message ID | 20221104074441.634677-1-chenxiaosong2@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] cifs: fix use-after-free on the link name | expand |
ChenXiaoSong <chenxiaosong2@huawei.com> writes: > 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> > --- > fs/cifs/cifsfs.c | 26 +++++++++++++++++++++++++- > fs/cifs/inode.c | 5 ----- > 2 files changed, 25 insertions(+), 6 deletions(-) Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
tentatively merged into cifs-2.6.git for-next pending additional testing On Fri, Nov 4, 2022 at 12:57 PM Paulo Alcantara via samba-technical <samba-technical@lists.samba.org> wrote: > > ChenXiaoSong <chenxiaosong2@huawei.com> writes: > > > 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> > > --- > > fs/cifs/cifsfs.c | 26 +++++++++++++++++++++++++- > > fs/cifs/inode.c | 5 ----- > > 2 files changed, 25 insertions(+), 6 deletions(-) > > Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz> >
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);
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> --- fs/cifs/cifsfs.c | 26 +++++++++++++++++++++++++- fs/cifs/inode.c | 5 ----- 2 files changed, 25 insertions(+), 6 deletions(-)