Affected: Linux, Siemens RUGGEDCOM RST2428P, Siemens SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 family, Siemens SCALANCE XCM-/XRM-/XCH-/XRH-300 family, Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem, Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP, Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP, Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

In the Linux kernel, the following vulnerability has been resolved:

tcp: check skb is non-NULL in tcp_rto_delta_us()

We have some machines running stock Ubuntu 20.04.6 which is their 5.4.0-174-generic kernel that are running ceph and recently hit a null ptr dereference in tcp_rearm_rto(). Initially hitting it from the TLP path, but then later we also saw it getting hit from the RACK case as well. Here are examples of the oops messages we saw in each of those cases:

Jul 26 15:05:02 rx [11061395.780353] BUG: kernel NULL pointer dereference, address: 0000000000000020 Jul 26 15:05:02 rx [11061395.787572] #PF: supervisor read access in kernel mode Jul 26 15:05:02 rx [11061395.792971] #PF: error_code(0x0000) - not-present page Jul 26 15:05:02 rx [11061395.798362] PGD 0 P4D 0 Jul 26 15:05:02 rx [11061395.801164] Oops: 0000 [#1] SMP NOPTI Jul 26 15:05:02 rx [11061395.805091] CPU: 0 PID: 9180 Comm: msgr-worker-1 Tainted: G W 5.4.0-174-generic #193-Ubuntu Jul 26 15:05:02 rx [11061395.814996] Hardware name: Supermicro SMC 2x26 os-gen8 64C NVME-Y 256G/H12SSW-NTR, BIOS 2.5.V1.2U.NVMe.UEFI 05/09/2023 Jul 26 15:05:02 rx [11061395.825952] RIP: 0010:tcp_rearm_rto+0xe4/0x160 Jul 26 15:05:02 rx [11061395.830656] Code: 87 ca 04 00 00 00 5b 41 5c 41 5d 5d c3 c3 49 8b bc 24 40 06 00 00 eb 8d 48 bb cf f7 53 e3 a5 9b c4 20 4c 89 ef e8 0c fe 0e 00 <48> 8b 78 20 48 c1 ef 03 48 89 f8 41 8b bc 24 80 04 00 00 48 f7 e3 Jul 26 15:05:02 rx [11061395.849665] RSP: 0018:ffffb75d40003e08 EFLAGS: 00010246 Ju…