ACK: [SRU][F/J/N/O][PATCH 0/2] CVE-2024-50047, CVE-2024-53185 and CVE-2025-37750

Fri May 23 09:25:26 UTC 2025

On 21.05.25 08:05, Massimiliano Pellizzer wrote:
> https://ubuntu.com/security/CVE-2024-50047
> https://ubuntu.com/security/CVE-2024-53185
> https://ubuntu.com/security/CVE-2025-37750
> 
> [ Impact ]
> 
> CVE-2024-50047
> 
> smb: client: fix UAF in async decryption
> 
> Doing an async decryption (large read) crashes with a
> slab-use-after-free way down in the crypto API.
> 
> This is because TFM is being used in parallel.
> 
> Fix this by allocating a new AEAD TFM for async decryption, but keep
> the existing one for synchronous READ cases (similar to what is done
> in smb3_calc_signature()).
> 
> Also remove the calls to aead_request_set_callback() and
> crypto_wait_req() since it's always going to be a synchronous operation.
> 
> CVE-2024-53185
> 
> smb: client: fix NULL ptr deref in crypto_aead_setkey()
> 
> Neither SMB3.0 or SMB3.02 supports encryption negotiate context, so
> when SMB2_GLOBAL_CAP_ENCRYPTION flag is set in the negotiate response,
> the client uses AES-128-CCM as the default cipher.  See MS-SMB2
> 3.3.5.4.
> 
> Commit b0abcd65ec54 ("smb: client: fix UAF in async decryption") added
> a @server->cipher_type check to conditionally call
> smb3_crypto_aead_allocate(), but that check would always be false as
> @server->cipher_type is unset for SMB3.02.
> 
> Fix this by setting @server->cipher_type for SMB3.02 as well.
> 
> CVE-2025-37750
> 
> smb: client: fix UAF in decryption with multichannel
> 
> After commit f7025d861694 ("smb: client: allocate crypto only for
> primary server") and commit b0abcd65ec54 ("smb: client: fix UAF in
> async decryption"), the channels started reusing AEAD TFM from primary
> channel to perform synchronous decryption, but that can't done as
> there could be multiple cifsd threads (one per channel) simultaneously
> accessing it to perform decryption.
> 
> [ Fix ]
> 
> Oracular and Noble:
>    Affected only by CVE-2025-37750,
>    backported the fix from mainline.
> Jammy and Focal:
>    Backported the fix for CVE-2024-50047
>    Cherry picked the fix for CVE-2024-53185
>    Backported the fix for CVE-2025-37750
> 
> [ Test Plan ]
> 
> Noble and Oracular compile tested only.
> 
> Jammy and Focal compile and boot tested.
> Moreover on Jammy and Focal I run the reprouducer
> and stress-ng using Jammy as a cifs server and
> Focal as a cifs client and vice versa.
> 
> # Server
> 
> $ sudo apt install -y samba
> 
> $ sudo mkdir -p /srv/smbshare
> $ sudo chmod 0777 /srv/smbshare
> 
> $ sudo adduser --disabled-password testuser
> $ sudo smbpasswd -a testuser
> 
> $ dd if=/dev/urandom of=/srv/smbshare/largefile bs=1M count=1024
> 
> Modified /etc/samba/smb.conf ensuring to have at lest the following:
> 
> [global]
>     server role = standalone server
>     smb encrypt = required
>     min protocol = SMB3
>     max protocol = SMB3_11
> 
> [sambashare]
>      path = /srv/smbshare
>      read only = no
>      browsable = yes
>      guest ok = no
>      valid users = testuser
> 
> $ sudo systemctl restart smbd
> 
> # Client
> 
> $ sudo apt install -y cifs-utils
> 
> $ sudo mkdir -p /mnt/smbshare
> $ sudo chmod 0777 /mnt/smbshare
> 
> $ sudo mount.cifs //10.10.10.25/sambashare /mnt/smbshare \
>      -o username=testuser,password=test,seal,vers=3.1.1,esize=1
>    
> $ dd if=/mnt/smbshare/largefile of=/dev/null bs=1M
> 1024+0 records in
> 1024+0 records out
> 1073741824 bytes (1.1 GB, 1.0 GiB) copied, 2.51368 s, 427 MB/s
> 
> $ cd /mnt/smbshare/
> $ sudo stress-ng --hdd 8 --hdd-bytes 2G --timeout 5m --verify --metrics-brief
> stress-ng: info:  [1379] setting to a 300 second (5 mins, 0.00 secs) run per stressor
> stress-ng: info:  [1379] dispatching hogs: 8 hdd
> stress-ng: info:  [1379] successful run completed in 300.18s (5 mins, 0.18 secs)
> stress-ng: info:  [1379] stressor       bogo ops real time  usr time  sys time   bogo ops/s     bogo ops/s
> stress-ng: info:  [1379]                           (secs)    (secs)    (secs)   (real time) (usr+sys time)
> stress-ng: info:  [1379] hdd              352025    300.15     17.46   1237.18      1172.82         280.58
> 
> All tests has been run  with KASAN enabled.
> 
> [ Where Problems Could Occur ]
> 
> The fix affects the SMB3 decryption logic in the CIFS client,
> specifically within the function used to process encrypted responses.
> An issue with this fix may lead to incorrect handling of per-thread
> cryptographic transform contexts (crypto_aead),
> particularly when offloaded decryption paths allocate
> and manage these contexts dynamically.
> A user might experience problems such as failed or corrupted file reads
> from encrypted SMB shares.
> 
> 
Acked-by: Stefan Bader <stefan.bader at canonical.com>
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