linux.git/fs/smb/client, branch v6.15

smb: client: Reset all search buffer pointers when releasing buffer

2025-05-20T01:29:06+00:00

Multiple pointers in struct cifs_search_info (ntwrk_buf_start,
srch_entries_start, and last_entry) point to the same allocated buffer.
However, when freeing this buffer, only ntwrk_buf_start was set to NULL,
while the other pointers remained pointing to freed memory.

This is defensive programming to prevent potential issues with stale
pointers. While the active UAF vulnerability is fixed by the previous
patch, this change ensures consistent pointer state and more robust error
handling.

Signed-off-by: Wang Zhaolong 
Cc: stable@vger.kernel.org
Reviewed-by: Paulo Alcantara (Red Hat) 
Signed-off-by: Steve French

smb: client: Fix use-after-free in cifs_fill_dirent

2025-05-18T21:53:06+00:00

There is a race condition in the readdir concurrency process, which may
access the rsp buffer after it has been released, triggering the
following KASAN warning.

 ==================================================================
 BUG: KASAN: slab-use-after-free in cifs_fill_dirent+0xb03/0xb60 [cifs]
 Read of size 4 at addr ffff8880099b819c by task a.out/342975

 CPU: 2 UID: 0 PID: 342975 Comm: a.out Not tainted 6.15.0-rc6+ #240 PREEMPT(full)
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014
 Call Trace:
  
  dump_stack_lvl+0x53/0x70
  print_report+0xce/0x640
  kasan_report+0xb8/0xf0
  cifs_fill_dirent+0xb03/0xb60 [cifs]
  cifs_readdir+0x12cb/0x3190 [cifs]
  iterate_dir+0x1a1/0x520
  __x64_sys_getdents+0x134/0x220
  do_syscall_64+0x4b/0x110
  entry_SYSCALL_64_after_hwframe+0x76/0x7e
 RIP: 0033:0x7f996f64b9f9
 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89
 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01
 f0 ff ff  0d f7 c3 0c 00 f7 d8 64 89 8
 RSP: 002b:00007f996f53de78 EFLAGS: 00000207 ORIG_RAX: 000000000000004e
 RAX: ffffffffffffffda RBX: 00007f996f53ecdc RCX: 00007f996f64b9f9
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
 RBP: 00007f996f53dea0 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000207 R12: ffffffffffffff88
 R13: 0000000000000000 R14: 00007ffc8cd9a500 R15: 00007f996f51e000
  

 Allocated by task 408:
  kasan_save_stack+0x20/0x40
  kasan_save_track+0x14/0x30
  __kasan_slab_alloc+0x6e/0x70
  kmem_cache_alloc_noprof+0x117/0x3d0
  mempool_alloc_noprof+0xf2/0x2c0
  cifs_buf_get+0x36/0x80 [cifs]
  allocate_buffers+0x1d2/0x330 [cifs]
  cifs_demultiplex_thread+0x22b/0x2690 [cifs]
  kthread+0x394/0x720
  ret_from_fork+0x34/0x70
  ret_from_fork_asm+0x1a/0x30

 Freed by task 342979:
  kasan_save_stack+0x20/0x40
  kasan_save_track+0x14/0x30
  kasan_save_free_info+0x3b/0x60
  __kasan_slab_free+0x37/0x50
  kmem_cache_free+0x2b8/0x500
  cifs_buf_release+0x3c/0x70 [cifs]
  cifs_readdir+0x1c97/0x3190 [cifs]
  iterate_dir+0x1a1/0x520
  __x64_sys_getdents64+0x134/0x220
  do_syscall_64+0x4b/0x110
  entry_SYSCALL_64_after_hwframe+0x76/0x7e

 The buggy address belongs to the object at ffff8880099b8000
  which belongs to the cache cifs_request of size 16588
 The buggy address is located 412 bytes inside of
  freed 16588-byte region [ffff8880099b8000, ffff8880099bc0cc)

 The buggy address belongs to the physical page:
 page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x99b8
 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
 anon flags: 0x80000000000040(head|node=0|zone=1)
 page_type: f5(slab)
 raw: 0080000000000040 ffff888001e03400 0000000000000000 dead000000000001
 raw: 0000000000000000 0000000000010001 00000000f5000000 0000000000000000
 head: 0080000000000040 ffff888001e03400 0000000000000000 dead000000000001
 head: 0000000000000000 0000000000010001 00000000f5000000 0000000000000000
 head: 0080000000000003 ffffea0000266e01 00000000ffffffff 00000000ffffffff
 head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
 page dumped because: kasan: bad access detected

 Memory state around the buggy address:
  ffff8880099b8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8880099b8100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 >ffff8880099b8180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                             ^
  ffff8880099b8200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8880099b8280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ==================================================================

POC is available in the link [1].

The problem triggering process is as follows:

Process 1                       Process 2
-----------------------------------------------------------------
cifs_readdir
  /* file->private_data == NULL */
  initiate_cifs_search
    cifsFile = kzalloc(sizeof(struct cifsFileInfo), GFP_KERNEL);
    smb2_query_dir_first ->query_dir_first()
      SMB2_query_directory
        SMB2_query_directory_init
        cifs_send_recv
        smb2_parse_query_directory
          srch_inf->ntwrk_buf_start = (char *)rsp;
          srch_inf->srch_entries_start = (char *)rsp + ...
          srch_inf->last_entry = (char *)rsp + ...
          srch_inf->smallBuf = true;
  find_cifs_entry
    /* if (cfile->srch_inf.ntwrk_buf_start) */
    cifs_small_buf_release(cfile->srch_inf // free

                        cifs_readdir  ->iterate_shared()
                          /* file->private_data != NULL */
                          find_cifs_entry
                            /* in while (...) loop */
                            smb2_query_dir_next  ->query_dir_next()
                              SMB2_query_directory
                                SMB2_query_directory_init
                                cifs_send_recv
                                  compound_send_recv
                                    smb_send_rqst
                                    __smb_send_rqst
                                      rc = -ERESTARTSYS;
                                      /* if (fatal_signal_pending()) */
                                      goto out;
                                      return rc
                            /* if (cfile->srch_inf.last_entry) */
                            cifs_save_resume_key()
                              cifs_fill_dirent // UAF
                            /* if (rc) */
                            return -ENOENT;

Fix this by ensuring the return code is checked before using pointers
from the srch_inf.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=220131 [1]
Fixes: a364bc0b37f1 ("[CIFS] fix saving of resume key before CIFSFindNext")
Cc: stable@vger.kernel.org
Reviewed-by: Paulo Alcantara (Red Hat) 
Signed-off-by: Wang Zhaolong 
Signed-off-by: Steve French

smb: client: fix zero rsize error messages

2025-05-15T00:26:38+00:00

cifs_prepare_read() might be called with a disconnected channel, where
TCP_Server_Info::max_read is set to zero due to reconnect, so calling
->negotiate_rize() will set @rsize to default min IO size (64KiB) and
then logging

	CIFS: VFS: SMB: Zero rsize calculated, using minimum value
	65536

If the reconnect happens in cifsd thread, cifs_renegotiate_iosize()
will end up being called and then @rsize set to the expected value.

Since we can't rely on the value of @server->max_read by the time we
call cifs_prepare_read(), try to ->negotiate_rize() only if
@cifs_sb->ctx->rsize is zero.

Reported-by: Steve French 
Fixes: c59f7c9661b9 ("smb: client: ensure aligned IO sizes")
Signed-off-by: Paulo Alcantara (Red Hat) 
Signed-off-by: Steve French

smb: client: fix memory leak during error handling for POSIX mkdir

2025-05-15T00:26:15+00:00

The response buffer for the CREATE request handled by smb311_posix_mkdir()
is leaked on the error path (goto err_free_rsp_buf) because the structure
pointer *rsp passed to free_rsp_buf() is not assigned until *after* the
error condition is checked.

As *rsp is initialised to NULL, free_rsp_buf() becomes a no-op and the leak
is instead reported by __kmem_cache_shutdown() upon subsequent rmmod of
cifs.ko if (and only if) the error path has been hit.

Pass rsp_iov.iov_base to free_rsp_buf() instead, similar to the code in
other functions in smb2pdu.c for which *rsp is assigned late.

Cc: stable@vger.kernel.org
Signed-off-by: Jethro Donaldson 
Signed-off-by: Steve French

smb: client: Avoid race in open_cached_dir with lease breaks

2025-05-07T20:24:46+00:00

A pre-existing valid cfid returned from find_or_create_cached_dir might
race with a lease break, meaning open_cached_dir doesn't consider it
valid, and thinks it's newly-constructed. This leaks a dentry reference
if the allocation occurs before the queued lease break work runs.

Avoid the race by extending holding the cfid_list_lock across
find_or_create_cached_dir and when the result is checked.

Cc: stable@vger.kernel.org
Reviewed-by: Henrique Carvalho 
Signed-off-by: Paul Aurich 
Signed-off-by: Steve French

smb3 client: warn when parse contexts returns error on compounded operation

2025-05-06T14:05:15+00:00

Coverity noticed that the rc on smb2_parse_contexts() was not being checked
in the case of compounded operations.  Since we don't want to stop parsing
the following compounded responses which are likely valid, we can't easily
error out here, but at least print a warning message if server has a bug
causing us to skip parsing the open response contexts.

Addresses-Coverity: 1639191
Acked-by: Paulo Alcantara (Red Hat) 
Signed-off-by: Steve French

smb: client: ensure aligned IO sizes

2025-05-01T13:35:58+00:00

Make all IO sizes multiple of PAGE_SIZE, either negotiated by the
server or passed through rsize, wsize and bsize mount options, to
prevent from breaking DIO reads and writes against servers that
enforce alignment as specified in MS-FSA 2.1.5.3 and 2.1.5.4.

Cc: linux-cifs@vger.kernel.org
Reviewed-by: David Howells 
Signed-off-by: Paulo Alcantara (Red Hat) 
Signed-off-by: Steve French

cifs: Fix changing times and read-only attr over SMB1 smb_set_file_info() function

2025-04-30T14:48:39+00:00

Function CIFSSMBSetPathInfo() is not supported by non-NT servers and
returns error. Fallback code via open filehandle and CIFSSMBSetFileInfo()
does not work neither because CIFS_open() works also only on NT server.

Therefore currently the whole smb_set_file_info() function as a SMB1
callback for the ->set_file_info() does not work with older non-NT SMB
servers, like Win9x and others.

This change implements fallback code in smb_set_file_info() which will
works with any server and allows to change time values and also to set or
clear read-only attributes.

To make existing fallback code via CIFSSMBSetFileInfo() working with also
non-NT servers, it is needed to change open function from CIFS_open()
(which is NT specific) to cifs_open_file() which works with any server
(this is just a open wrapper function which choose the correct open
function supported by the server).

CIFSSMBSetFileInfo() is working also on non-NT servers, but zero time
values are not treated specially. So first it is needed to fill all time
values if some of them are missing, via cifs_query_path_info() call.

There is another issue, opening file in write-mode (needed for changing
attributes) is not possible when the file has read-only attribute set.
The only option how to clear read-only attribute is via SMB_COM_SETATTR
command. And opening directory is not possible neither and here the
SMB_COM_SETATTR command is the only option how to change attributes.
And CIFSSMBSetFileInfo() does not honor setting read-only attribute, so
for setting is also needed to use SMB_COM_SETATTR command.

Existing code in cifs_query_path_info() is already using SMB_COM_GETATTR as
a fallback code path (function SMBQueryInformation()), so introduce a new
function SMBSetInformation which will implement SMB_COM_SETATTR command.

My testing showed that Windows XP SMB1 client is also using SMB_COM_SETATTR
command for setting or clearing read-only attribute against non-NT server.
So this can prove that this is the correct way how to do it.

With this change it is possible set all 4 time values and all attributes,
including clearing and setting read-only bit on non-NT SMB servers.
Tested against Win98 SMB1 server.

This change fixes "touch" command which was failing when called on existing
file. And fixes also "chmod +w" and "chmod -w" commands which were also
failing (as they are changing read-only attribute).

Note that this change depends on following change
"cifs: Improve cifs_query_path_info() and cifs_query_file_info()"
as it require to query all 4 time attribute values.

Signed-off-by: Pali Rohár 
Signed-off-by: Steve French

cifs: Fix and improve cifs_query_path_info() and cifs_query_file_info()

2025-04-30T14:48:39+00:00

When CAP_NT_SMBS was not negotiated then do not issue CIFSSMBQPathInfo()
and CIFSSMBQFileInfo() commands. CIFSSMBQPathInfo() is not supported by
non-NT Win9x SMB server and CIFSSMBQFileInfo() returns from Win9x SMB
server bogus data in Attributes field (for example lot of files are marked
as reparse points, even Win9x does not support them and read-only bit is
not marked for read-only files). Correct information is returned by
CIFSFindFirst() or SMBQueryInformation() command.

So as a fallback in cifs_query_path_info() function use CIFSFindFirst()
with SMB_FIND_FILE_FULL_DIRECTORY_INFO level which is supported by both NT
and non-NT servers and as a last option use SMBQueryInformation() as it was
before.

And in function cifs_query_file_info() immediately returns -EOPNOTSUPP when
not communicating with NT server. Client then revalidate inode entry by the
cifs_query_path_info() call, which is working fine. So fstat() syscall on
already opened file will receive correct information.

Note that both fallback functions in non-UNICODE mode expands wildcards.
Therefore those fallback functions cannot be used on paths which contain
SMB wildcard characters (* ? " > <).

CIFSFindFirst() returns all 4 time attributes as opposite of
SMBQueryInformation() which returns only one.

With this change it is possible to query all 4 times attributes from Win9x
server and at the same time, client minimize sending of unsupported
commands to server.

Signed-off-by: Pali Rohár 
Signed-off-by: Steve French

smb: client: fix zero length for mkdir POSIX create context

2025-04-30T14:48:27+00:00

SMB create requests issued via smb311_posix_mkdir() have an incorrect
length of zero bytes for the POSIX create context data. ksmbd server
rejects such requests and logs "cli req too short" causing mkdir to fail
with "invalid argument" on the client side.  It also causes subsequent
rmmod to crash in cifs_destroy_request_bufs()

Inspection of packets sent by cifs.ko using wireshark show valid data for
the SMB2_POSIX_CREATE_CONTEXT is appended with the correct offset, but
with an incorrect length of zero bytes. Fails with ksmbd+cifs.ko only as
Windows server/client does not use POSIX extensions.

Fix smb311_posix_mkdir() to set req->CreateContextsLength as part of
appending the POSIX creation context to the request.

Signed-off-by: Jethro Donaldson 
Acked-by: Paulo Alcantara (Red Hat) 
Reviewed-by: Namjae Jeon 
Cc: stable@vger.kernel.org
Signed-off-by: Steve French