CVE-2026-23406

In the Linux kernel, the following vulnerability has been resolved:  apparmor: fix side-effect bug in matchchar() macro usage  The matchchar() macro evaluates its character parameter multiple times when traversing differential encoding chains. When invoked with *str++, the string pointer advances on each iteration of the inner do-while loop, causing the DFA to check different characters at each iteration and therefore skip input characters. This results in out-of-bounds reads when the pointer advances past the input buffer boundary.  [   94.984676] ================================================================== [   94.985301] BUG: KASAN: slab-out-of-bounds in aadfamatch+0x5ae/0x760 [   94.985655] Read of size 1 at addr ffff888100342000 by task file/976  [   94.986319] CPU: 7 UID: 1000 PID: 976 Comm: file Not tainted 6.19.0-rc7-next-20260127 #1 PREEMPT(lazy) [   94.986322] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [   94.986329] Call Trace: [   94.986341]  <TASK> [   94.986347]  dumpstacklvl+0x5e/0x80 [   94.986374]  printreport+0xc8/0x270 [   94.986384]  ? aadfamatch+0x5ae/0x760 [   94.986388]  kasanreport+0x118/0x150 [   94.986401]  ? aadfamatch+0x5ae/0x760 [   94.986405]  aadfamatch+0x5ae/0x760 [   94.986408]  _aapathperm+0x131/0x400 [   94.986418]  aapathperm+0x219/0x2f0 [   94.986424]  apparmorfileopen+0x345/0x570 [   94.986431]  securityfileopen+0x5c/0x140 [   94.986442]  dodentryopen+0x2f6/0x1120 [   94.986450]  vfsopen+0x38/0x2b0 [   94.986453]  ? mayopen+0x1e2/0x2b0 [   94.986466]  pathopenat+0x231b/0x2b30 [   94.986469]  ? x64sysopenat+0xf8/0x130 [   94.986477]  dofileopen+0x19d/0x360 [   94.986487]  dosysopenat2+0x98/0x100 [   94.986491]  x64sysopenat+0xf8/0x130 [   94.986499]  dosyscall64+0x8e/0x660 [   94.986515]  ? countmemcgevents+0x15f/0x3c0 [   94.986526]  ? srsoaliasreturnthunk+0x5/0xfbef5 [   94.986540]  ? handlemmfault+0x1639/0x1ef0 [   94.986551]  ? vmastartread+0xf0/0x320 [   94.986558]  ? srsoaliasreturnthunk+0x5/0xfbef5 [   94.986561]  ? srsoaliasreturnthunk+0x5/0xfbef5 [   94.986563]  ? fpregsassertstateconsistent+0x50/0xe0 [   94.986572]  ? srsoaliasreturnthunk+0x5/0xfbef5 [   94.986574]  ? archexittousermodeprepare+0x9/0xb0 [   94.986587]  ? srsoaliasreturnthunk+0x5/0xfbef5 [   94.986588]  ? irqentryexit+0x3c/0x590 [   94.986595]  entrySYSCALL64afterhwframe+0x76/0x7e [   94.986597] RIP: 0033:0x7fda4a79c3ea  Fix by extracting the character value before invoking match_char, ensuring single evaluation per outer loop.