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| author |   ChenXiaoSong <chenxiaosong2@huawei.com> | 2022-11-04 15:44:41 +0800 |
|---|---|---|
| committer |   Steve French <stfrench@microsoft.com> | 2022-11-04 23:36:54 -0500 |
| commit | 542228db2f28fdf775b301f2843e1fe486e7c797 (patch) | |
| tree | 60ed90760ffef328e87d4da2c44a5b7ff2587e3c /fs/cifs | |
| parent | cifs: avoid unnecessary iteration of tcp sessions (diff) | |
| download | linux-dev-542228db2f28fdf775b301f2843e1fe486e7c797.tar.xz linux-dev-542228db2f28fdf775b301f2843e1fe486e7c797.zip | |
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>
Diffstat (limited to 'fs/cifs')
| -rw-r--r-- | fs/cifs/cifsfs.c | 26 | ||||
| -rw-r--r-- | fs/cifs/inode.c | 5 |
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); |