UBUNTU-CVE-2026-23427: Use After Free

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in durable v2 replay of active file handles parsedurablehandlecontext() unconditionally assigns dhinfo->fp->conn to the current connection when handling a DURABLEREQV2 context with SMB2FLAGSREPLAYOPERATION. ksmbdlookupfdcguid() does not filter by fp->conn, so it returns file handles that are already actively connected. The unconditional overwrite replaces fp->conn, and when the overwriting connection is subsequently freed, ksmbdclosefd() dereferences the stale fp->conn via spinlock(&fp->conn->llistlock), causing a use-after-free. KASAN report: [ 7.349357] ================================================================== [ 7.349607] BUG: KASAN: slab-use-after-free in rawspinlock+0x75/0xe0 [ 7.349811] Write of size 4 at addr ffff8881056ac18c by task kworker/1:2/108 [ 7.350010] [ 7.350064] CPU: 1 UID: 0 PID: 108 Comm: kworker/1:2 Not tainted 7.0.0-rc3+ #58 PREEMPTLAZY [ 7.350068] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, archcaps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 7.350070] Workqueue: ksmbd-io handleksmbdwork [ 7.350083] Call Trace: [ 7.350087] <TASK> [ 7.350087] dumpstacklvl+0x64/0x80 [ 7.350094] printreport+0xce/0x660 [ 7.350100] ? pfxrawspinlockirqsave+0x10/0x10 [ 7.350101] ? pfxmodtimer+0x10/0x10 [ 7.350106] ? rawspinlock+0x75/0xe0 [ 7.350108] kasanreport+0xce/0x100 [ 7.350109] ? rawspinlock+0x75/0xe0 [ 7.350114] kasancheckrange+0x105/0x1b0 [ 7.350116] rawspinlock+0x75/0xe0 [ 7.350118] ? pfxrawspinlock+0x10/0x10 [ 7.350119] ? callrcucommon.constprop.0+0x25e/0x780 [ 7.350125] ? closeiddeloplock+0x2cc/0x4e0 [ 7.350128] ksmbdclosefd+0x27f/0xaf0 [ 7.350131] ksmbdclosefd+0x135/0x1b0 [ 7.350133] smb2close+0xb19/0x15b0 [ 7.350142] ? pfxsmb2close+0x10/0x10 [ 7.350143] ? xasload+0x18/0x270 [ 7.350146] ? rawspinlock+0x84/0xe0 [ 7.350148] ? pfxrawspinlock+0x10/0x10 [ 7.350150] ? rawspinunlock+0xe/0x30 [ 7.350151] ? ksmbdsmb2checkmessage+0xeb2/0x24c0 [ 7.350153] ? ksmbdtreeconnlookup+0xcd/0xf0 [ 7.350154] handleksmbdwork+0x40f/0x1080 [ 7.350156] processonework+0x5fa/0xef0 [ 7.350162] ? assignwork+0x122/0x3e0 [ 7.350163] workerthread+0x54b/0xf70 [ 7.350165] ? pfxworkerthread+0x10/0x10 [ 7.350166] kthread+0x346/0x470 [ 7.350170] ? recalcsigpending+0x19b/0x230 [ 7.350176] ? pfxkthread+0x10/0x10 [ 7.350178] retfromfork+0x4fb/0x6c0 [ 7.350183] ? pfxretfromfork+0x10/0x10 [ 7.350185] ? switchto+0x36c/0xbe0 [ 7.350188] ? pfxkthread+0x10/0x10 [ 7.350190] retfromforkasm+0x1a/0x30 [ 7.350197] </TASK> [ 7.350197] [ 7.355160] Allocated by task 123: [ 7.355261] kasansavestack+0x33/0x60 [ 7.355373] kasansavetrack+0x14/0x30 [ 7.355484] kasankmalloc+0x8f/0xa0 [ 7.355593] ksmbdconnalloc+0x44/0x6d0 [ 7.355711] ksmbdkthreadfn+0x243/0xd70 [ 7.355839] kthread+0x346/0x470 [ 7.355942] retfromfork+0x4fb/0x6c0 [ 7.356051] retfromforkasm+0x1a/0x30 [ 7.356164] [ 7.356214] Freed by task 134: [ 7.356305] kasansavestack+0x33/0x60 [ 7.356416] kasansavetrack+0x14/0x30 [ 7.356527] kasansavefreeinfo+0x3b/0x60 [ 7.356646] kasanslabfree+0x43/0x70 [ 7.356761] kfree+0x1ca/0x430 [ 7.356862] ksmbdtcpdisconnect+0x59/0xe0 [ 7.356993] ksmbdconnhandlerloop+0x77e/0xd40 [ 7.357138] kthread+0x346/0x470 [ 7.357240] retfromfork+0x4fb/0x6c0 [ 7.357350] retfromforkasm+0x1a/0x30 [ 7.357463] [ 7.357513] The buggy address belongs to the object at ffff8881056ac000 [ 7.357513] which belongs to the cache kmalloc-1k of size 1024 [ 7.357857] The buggy address is located 396 bytes inside of [ 7.357857] freed 1024-byte region ---truncated---