When using encryption, either enforced by the server or when using
'seal' mount option, the client will squash all compound request buffers
down for encryption into a single iov in smb2_set_next_command().
SMB2_ioctl_init() allocates a small buffer (448 bytes) to hold the
SMB2_IOCTL request in the first iov, and if the user passes an input
buffer that is greater than 328 bytes, smb2_set_next_command() will
end up writing off the end of @rqst->iov[0].iov_base as shown below:
mount.cifs //srv/share /mnt -o ...,seal
ln -s $(perl -e "print('a')for 1..1024") /mnt/link
BUG: KASAN: slab-out-of-bounds in
smb2_set_next_command.cold+0x1d6/0x24c [cifs]
Write of size 4116 at addr ffff8881148fcab8 by task ln/859
CPU: 1 UID: 0 PID: 859 Comm: ln Not tainted 6.12.0-rc3 #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
1.16.3-2.fc40 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x5d/0x80
? smb2_set_next_command.cold+0x1d6/0x24c [cifs]
print_report+0x156/0x4d9
? smb2_set_next_command.cold+0x1d6/0x24c [cifs]
? __virt_addr_valid+0x145/0x310
? __phys_addr+0x46/0x90
? smb2_set_next_command.cold+0x1d6/0x24c [cifs]
kasan_report+0xda/0x110
? smb2_set_next_command.cold+0x1d6/0x24c [cifs]
kasan_check_range+0x10f/0x1f0
__asan_memcpy+0x3c/0x60
smb2_set_next_command.cold+0x1d6/0x24c [cifs]
smb2_compound_op+0x238c/0x3840 [cifs]
? kasan_save_track+0x14/0x30
? kasan_save_free_info+0x3b/0x70
? vfs_symlink+0x1a1/0x2c0
? do_symlinkat+0x108/0x1c0
? __pfx_smb2_compound_op+0x10/0x10 [cifs]
? kmem_cache_free+0x118/0x3e0
? cifs_get_writable_path+0xeb/0x1a0 [cifs]
smb2_get_reparse_inode+0x423/0x540 [cifs]
? __pfx_smb2_get_reparse_inode+0x10/0x10 [cifs]
? rcu_is_watching+0x20/0x50
? __kmalloc_noprof+0x37c/0x480
? smb2_create_reparse_symlink+0x257/0x490 [cifs]
? smb2_create_reparse_symlink+0x38f/0x490 [cifs]
smb2_create_reparse_symlink+0x38f/0x490 [cifs]
? __pfx_smb2_create_reparse_symlink+0x10/0x10 [cifs]
? find_held_lock+0x8a/0xa0
? hlock_class+0x32/0xb0
? __build_path_from_dentry_optional_prefix+0x19d/0x2e0 [cifs]
cifs_symlink+0x24f/0x960 [cifs]
? __pfx_make_vfsuid+0x10/0x10
? __pfx_cifs_symlink+0x10/0x10 [cifs]
? make_vfsgid+0x6b/0xc0
? generic_permission+0x96/0x2d0
vfs_symlink+0x1a1/0x2c0
do_symlinkat+0x108/0x1c0
? __pfx_do_symlinkat+0x10/0x10
? strncpy_from_user+0xaa/0x160
__x64_sys_symlinkat+0xb9/0xf0
do_syscall_64+0xbb/0x1d0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f08d75c13bb
Reported-by: David Howells <dhowells@xxxxxxxxxx>
Fixes: e77fe73c7e38 ("cifs: we can not use small padding iovs together with encryption")
Signed-off-by: Paulo Alcantara (Red Hat) <pc@xxxxxxxxxxxxx>
---
fs/smb/client/smb2pdu.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
index b2f16a7b696d..069bbfdc9750 100644
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -3313,6 +3313,16 @@ SMB2_ioctl_init(struct cifs_tcon *tcon, struct TCP_Server_Info *server,
return rc;
if (indatalen) {
+ unsigned int len;
+
+ pr_err("XXX %s: total_len=%u\n", __func__, total_len - 1);
+ if (WARN_ON_ONCE(smb3_encryption_required(tcon) &&
+ (check_add_overflow(total_len - 1,
+ ALIGN(indatalen, 8), &len) ||
+ len > MAX_CIFS_SMALL_BUFFER_SIZE))) {
+ cifs_small_buf_release(req);
+ return -EIO;
+ }
/*
* indatalen is usually small at a couple of bytes max, so
* just allocate through generic pool
--
2.47.0
