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

ksmbd: unset the binding mark of a reused connection

Steve French reported null pointer dereference error from sha256 lib. cifs.ko can send session setup requests on reused connection. If reused connection is used for binding session, conn->binding can still remain true and generatepreauthhash() will not set sess->PreauthHashValue and it will be NULL. It is used as a material to create an encryption key in ksmbdgensmb311encryptionkey. ->PreauthHashValue cause null pointer dereference error from cryptoshash_update().

BUG: kernel NULL pointer dereference, address: 0000000000000000

PF: supervisor read access in kernel mode

PF: error_code(0x0000) - not-present page

PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 8 PID: 429254 Comm: kworker/8:39 Hardware name: LENOVO 20MAS08500/20MAS08500, BIOS N2CET69W (1.52 ) Workqueue: ksmbd-io handleksmbdwork [ksmbd] RIP: 0010:libsha256basedoupdate.isra.0+0x11e/0x1d0 [sha256ssse3] <TASK> ? showregs+0x6d/0x80 ? _die+0x24/0x80 ? pagefaultoops+0x99/0x1b0 ? douseraddrfault+0x2ee/0x6b0 ? excpagefault+0x83/0x1b0 ? asmexcpagefault+0x27/0x30 ? _pfxsha256transformrorx+0x10/0x10 [sha256ssse3] ? libsha256basedoupdate.isra.0+0x11e/0x1d0 [sha256ssse3] ? _pfxsha256transformrorx+0x10/0x10 [sha256ssse3] ? _pfxsha256transformrorx+0x10/0x10 [sha256ssse3] _sha256update+0x77/0xa0 [sha256ssse3] sha256avx2update+0x15/0x30 [sha256ssse3] cryptoshashupdate+0x1e/0x40 hmacupdate+0x12/0x20 cryptoshashupdate+0x1e/0x40 generatekey+0x234/0x380 [ksmbd] generatesmb3encryptionkey+0x40/0x1c0 [ksmbd] ksmbdgensmb311encryptionkey+0x72/0xa0 [ksmbd] ntlmauthenticate.isra.0+0x423/0x5d0 [ksmbd] smb2sesssetup+0x952/0xaa0 [ksmbd] _processrequest+0xa3/0x1d0 [ksmbd] _handleksmbdwork+0x1c4/0x2f0 [ksmbd] handleksmbdwork+0x2d/0xa0 [ksmbd] processonework+0x16c/0x350 workerthread+0x306/0x440 ? _pfxworkerthread+0x10/0x10 kthread+0xef/0x120 ? _pfxkthread+0x10/0x10 retfromfork+0x44/0x70 ? _pfxkthread+0x10/0x10 retfromfork_asm+0x1b/0x30 </TASK>