{"id":"AZL-59651","summary":"CVE-2025-21999 affecting package kernel for versions less than 6.6.85.1-2","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nproc: fix UAF in proc_get_inode()\n\nFix race between rmmod and /proc/XXX's inode instantiation.\n\nThe bug is that pde-\u003eproc_ops don't belong to /proc, it belongs to a\nmodule, therefore dereferencing it after /proc entry has been registered\nis a bug unless use_pde/unuse_pde() pair has been used.\n\nuse_pde/unuse_pde can be avoided (2 atomic ops!) because pde-\u003eproc_ops\nnever changes so information necessary for inode instantiation can be\nsaved _before_ proc_register() in PDE itself and used later, avoiding\npde-\u003eproc_ops-\u003e...  dereference.\n\n      rmmod                         lookup\nsys_delete_module\n                         proc_lookup_de\n\t\t\t   pde_get(de);\n\t\t\t   proc_get_inode(dir-\u003ei_sb, de);\n  mod-\u003eexit()\n    proc_remove\n      remove_proc_subtree\n       proc_entry_rundown(de);\n  free_module(mod);\n\n                               if (S_ISREG(inode-\u003ei_mode))\n\t                         if (de-\u003eproc_ops-\u003eproc_read_iter)\n                           --\u003e As module is already freed, will trigger UAF\n\nBUG: unable to handle page fault for address: fffffbfff80a702b\nPGD 817fc4067 P4D 817fc4067 PUD 817fc0067 PMD 102ef4067 PTE 0\nOops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI\nCPU: 26 UID: 0 PID: 2667 Comm: ls Tainted: G\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996)\nRIP: 0010:proc_get_inode+0x302/0x6e0\nRSP: 0018:ffff88811c837998 EFLAGS: 00010a06\nRAX: dffffc0000000000 RBX: ffffffffc0538140 RCX: 0000000000000007\nRDX: 1ffffffff80a702b RSI: 0000000000000001 RDI: ffffffffc0538158\nRBP: ffff8881299a6000 R08: 0000000067bbe1e5 R09: 1ffff11023906f20\nR10: ffffffffb560ca07 R11: ffffffffb2b43a58 R12: ffff888105bb78f0\nR13: ffff888100518048 R14: ffff8881299a6004 R15: 0000000000000001\nFS:  00007f95b9686840(0000) GS:ffff8883af100000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: fffffbfff80a702b CR3: 0000000117dd2000 CR4: 00000000000006f0\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\nCall Trace:\n \u003cTASK\u003e\n proc_lookup_de+0x11f/0x2e0\n __lookup_slow+0x188/0x350\n walk_component+0x2ab/0x4f0\n path_lookupat+0x120/0x660\n filename_lookup+0x1ce/0x560\n vfs_statx+0xac/0x150\n __do_sys_newstat+0x96/0x110\n do_syscall_64+0x5f/0x170\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\n[adobriyan@gmail.com: don't do 2 atomic ops on the common path]","modified":"2026-04-01T05:19:31.823106Z","published":"2025-04-03T08:15:15Z","upstream":["CVE-2025-21999"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21999"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.6.85.1-2"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-59651.json"}}],"schema_version":"1.7.5"}