{"id":"DEBIAN-CVE-2024-56693","details":"In the Linux kernel, the following vulnerability has been resolved:  brd: defer automatic disk creation until module initialization succeeds  My colleague Wupeng found the following problems during fault injection:  BUG: unable to handle page fault for address: fffffbfff809d073 PGD 6e648067 P4D 123ec8067 PUD 123ec4067 PMD 100e38067 PTE 0 Oops: Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI CPU: 5 UID: 0 PID: 755 Comm: modprobe Not tainted 6.12.0-rc3+ #17 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:__asan_load8+0x4c/0xa0 ... Call Trace:  \u003cTASK\u003e  blkdev_put_whole+0x41/0x70  bdev_release+0x1a3/0x250  blkdev_release+0x11/0x20  __fput+0x1d7/0x4a0  task_work_run+0xfc/0x180  syscall_exit_to_user_mode+0x1de/0x1f0  do_syscall_64+0x6b/0x170  entry_SYSCALL_64_after_hwframe+0x76/0x7e  loop_init() is calling loop_add() after __register_blkdev() succeeds and is ignoring disk_add() failure from loop_add(), for loop_add() failure is not fatal and successfully created disks are already visible to bdev_open().  brd_init() is currently calling brd_alloc() before __register_blkdev() succeeds and is releasing successfully created disks when brd_init() returns an error. This can cause UAF for the latter two case:  case 1:     T1: modprobe brd   brd_init     brd_alloc(0) // success       add_disk         disk_scan_partitions           bdev_file_open_by_dev // alloc file           fput // won't free until back to userspace     brd_alloc(1) // failed since mem alloc error inject   // error path for modprobe will release code segment   // back to userspace   __fput     blkdev_release       bdev_release         blkdev_put_whole           bdev-\u003ebd_disk-\u003efops-\u003erelease // fops is freed now, UAF!  case 2:     T1:                            T2: modprobe brd   brd_init     brd_alloc(0) // success                                    open(/dev/ram0)     brd_alloc(1) // fail   // error path for modprobe                                     close(/dev/ram0)                                    ...                                    /* UAF! */                                    bdev-\u003ebd_disk-\u003efops-\u003erelease  Fix this problem by following what loop_init() does. Besides, reintroduce brd_devices_mutex to help serialize modifications to brd_list.","modified":"2026-09-15T09:03:17.301258115Z","published":"2024-12-28T10:15:14.833Z","upstream":["CVE-2024-56693"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2024-56693"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.123-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-56693.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.3-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-56693.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.3-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-56693.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}