ghsa-8jvx-wqf8-m6ph
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
cachefiles: fix slab-use-after-free in cachefiles_ondemand_get_fd()
We got the following issue in a fuzz test of randomly issuing the restore command:
================================================================== BUG: KASAN: slab-use-after-free in cachefiles_ondemand_daemon_read+0x609/0xab0 Write of size 4 at addr ffff888109164a80 by task ondemand-04-dae/4962
CPU: 11 PID: 4962 Comm: ondemand-04-dae Not tainted 6.8.0-rc7-dirty #542 Call Trace: kasan_report+0x94/0xc0 cachefiles_ondemand_daemon_read+0x609/0xab0 vfs_read+0x169/0xb50 ksys_read+0xf5/0x1e0
Allocated by task 626: __kmalloc+0x1df/0x4b0 cachefiles_ondemand_send_req+0x24d/0x690 cachefiles_create_tmpfile+0x249/0xb30 cachefiles_create_file+0x6f/0x140 cachefiles_look_up_object+0x29c/0xa60 cachefiles_lookup_cookie+0x37d/0xca0 fscache_cookie_state_machine+0x43c/0x1230 [...]
Freed by task 626: kfree+0xf1/0x2c0 cachefiles_ondemand_send_req+0x568/0x690 cachefiles_create_tmpfile+0x249/0xb30 cachefiles_create_file+0x6f/0x140 cachefiles_look_up_object+0x29c/0xa60 cachefiles_lookup_cookie+0x37d/0xca0 fscache_cookie_state_machine+0x43c/0x1230 [...] ==================================================================
Following is the process that triggers the issue:
mount | daemon_thread1 | daemon_thread2
cachefiles_ondemand_init_object cachefiles_ondemand_send_req REQ_A = kzalloc(sizeof(*req) + data_len) wait_for_completion(&REQ_A->done)
cachefiles_daemon_read
cachefiles_ondemand_daemon_read
REQ_A = cachefiles_ondemand_select_req
cachefiles_ondemand_get_fd
copy_to_user(_buffer, msg, n)
process_open_req(REQ_A)
------ restore ------
cachefiles_ondemand_restore
xas_for_each(&xas, req, ULONG_MAX)
xas_set_mark(&xas, CACHEFILES_REQ_NEW);
cachefiles_daemon_read
cachefiles_ondemand_daemon_read
REQ_A = cachefiles_ondemand_select_req
write(devfd, ("copen %u,%llu", msg->msg_id, size));
cachefiles_ondemand_copen
xa_erase(&cache->reqs, id)
complete(&REQ_A->done)
kfree(REQ_A) cachefiles_ondemand_get_fd(REQ_A) fd = get_unused_fd_flags file = anon_inode_getfile fd_install(fd, file) load = (void *)REQ_A->msg.data; load->fd = fd; // load UAF !!!
This issue is caused by issuing a restore command when the daemon is still alive, which results in a request being processed multiple times thus triggering a UAF. So to avoid this problem, add an additional reference count to cachefiles_req, which is held while waiting and reading, and then released when the waiting and reading is over.
Note that since there is only one reference count for waiting, we need to avoid the same request being completed multiple times, so we can only complete the request if it is successfully removed from the xarray.
{
"affected": [],
"aliases": [
"CVE-2024-40899"
],
"database_specific": {
"cwe_ids": [
"CWE-416"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-07-12T13:15:13Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncachefiles: fix slab-use-after-free in cachefiles_ondemand_get_fd()\n\nWe got the following issue in a fuzz test of randomly issuing the restore\ncommand:\n\n==================================================================\nBUG: KASAN: slab-use-after-free in cachefiles_ondemand_daemon_read+0x609/0xab0\nWrite of size 4 at addr ffff888109164a80 by task ondemand-04-dae/4962\n\nCPU: 11 PID: 4962 Comm: ondemand-04-dae Not tainted 6.8.0-rc7-dirty #542\nCall Trace:\n kasan_report+0x94/0xc0\n cachefiles_ondemand_daemon_read+0x609/0xab0\n vfs_read+0x169/0xb50\n ksys_read+0xf5/0x1e0\n\nAllocated by task 626:\n __kmalloc+0x1df/0x4b0\n cachefiles_ondemand_send_req+0x24d/0x690\n cachefiles_create_tmpfile+0x249/0xb30\n cachefiles_create_file+0x6f/0x140\n cachefiles_look_up_object+0x29c/0xa60\n cachefiles_lookup_cookie+0x37d/0xca0\n fscache_cookie_state_machine+0x43c/0x1230\n [...]\n\nFreed by task 626:\n kfree+0xf1/0x2c0\n cachefiles_ondemand_send_req+0x568/0x690\n cachefiles_create_tmpfile+0x249/0xb30\n cachefiles_create_file+0x6f/0x140\n cachefiles_look_up_object+0x29c/0xa60\n cachefiles_lookup_cookie+0x37d/0xca0\n fscache_cookie_state_machine+0x43c/0x1230\n [...]\n==================================================================\n\nFollowing is the process that triggers the issue:\n\n mount | daemon_thread1 | daemon_thread2\n------------------------------------------------------------\n cachefiles_ondemand_init_object\n cachefiles_ondemand_send_req\n REQ_A = kzalloc(sizeof(*req) + data_len)\n wait_for_completion(\u0026REQ_A-\u003edone)\n\n cachefiles_daemon_read\n cachefiles_ondemand_daemon_read\n REQ_A = cachefiles_ondemand_select_req\n cachefiles_ondemand_get_fd\n copy_to_user(_buffer, msg, n)\n process_open_req(REQ_A)\n ------ restore ------\n cachefiles_ondemand_restore\n xas_for_each(\u0026xas, req, ULONG_MAX)\n xas_set_mark(\u0026xas, CACHEFILES_REQ_NEW);\n\n cachefiles_daemon_read\n cachefiles_ondemand_daemon_read\n REQ_A = cachefiles_ondemand_select_req\n\n write(devfd, (\"copen %u,%llu\", msg-\u003emsg_id, size));\n cachefiles_ondemand_copen\n xa_erase(\u0026cache-\u003ereqs, id)\n complete(\u0026REQ_A-\u003edone)\n kfree(REQ_A)\n cachefiles_ondemand_get_fd(REQ_A)\n fd = get_unused_fd_flags\n file = anon_inode_getfile\n fd_install(fd, file)\n load = (void *)REQ_A-\u003emsg.data;\n load-\u003efd = fd;\n // load UAF !!!\n\nThis issue is caused by issuing a restore command when the daemon is still\nalive, which results in a request being processed multiple times thus\ntriggering a UAF. So to avoid this problem, add an additional reference\ncount to cachefiles_req, which is held while waiting and reading, and then\nreleased when the waiting and reading is over.\n\nNote that since there is only one reference count for waiting, we need to\navoid the same request being completed multiple times, so we can only\ncomplete the request if it is successfully removed from the xarray.",
"id": "GHSA-8jvx-wqf8-m6ph",
"modified": "2024-08-28T21:31:27Z",
"published": "2024-07-12T15:31:26Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-40899"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1d902d9a3aa4f2a8bda698294e34be788be012fc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/99e9c5bd27ddefa0f9db88625bf5e31c1e833d62"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a6de82765e12fb1201ab607f0d3ffe3309b30fc0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/de3e26f9e5b76fc628077578c001c4a51bf54d06"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
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