CVE-2026-63809

*** Pendiente de traducción *** In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> bpf: use kvfree() for replaced sysctl write buffer<br /> <br /> proc_sys_call_handler() allocates its temporary sysctl buffer with<br /> kvzalloc() and passes it to __cgroup_bpf_run_filter_sysctl(). Since<br /> kvzalloc() may fall back to vmalloc() for large allocations, freeing<br /> that buffer with kfree() is wrong and can corrupt memory.<br /> <br /> Use kvfree() to safely handle both kmalloc and kvzalloc()/vmalloc<br /> allocations.<br /> <br /> The bug was first flagged by an experimental analysis tool we are<br /> developing for kernel memory-management bugs while analyzing<br /> v6.13-rc1. The tool is still under development and is not yet publicly<br /> available. Manual inspection confirms that the bug is still<br /> present in v7.1-rc5.<br /> <br /> Reproduced the bug based on v7.1-rc4 in a QEMU x86_64 guest booted with<br /> KASAN and CONFIG_FAILSLAB enabled. To exercise the replacement path, the<br /> test tree also included the accompanying fix for the stale ret == 1<br /> check in __cgroup_bpf_run_filter_sysctl(). The reproducer confines<br /> failslab injections to the proc_sys_call_handler() range, uses<br /> stacktrace-depth=32, and injects fail-nth=1 while writing 8191 bytes to<br /> /proc/sys/kernel/domainname from a task in the target cgroup. Under<br /> that setup, fail-nth=1 triggered the fault:<br /> <br /> BUG: unable to handle page fault for address: ffffeb0200024d48<br /> #PF: supervisor read access in kernel mode<br /> #PF: error_code(0x0000) - not-present page<br /> PGD 0 P4D 0<br /> Oops: Oops: 0000 SMP KASAN NOPTI<br /> CPU: 2 UID: 0 PID: 209 Comm: repro_proc_sys_ Not tainted 7.1.0-rc4-00686-g97625979a5d4 PREEMPT(lazy)<br /> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014<br /> RIP: 0010:kfree+0x6e/0x510<br /> ...<br /> Call Trace:<br /> <br /> ? __cgroup_bpf_run_filter_sysctl+0x626/0xc30<br /> __cgroup_bpf_run_filter_sysctl+0x74d/0xc30<br /> ? __pfx___cgroup_bpf_run_filter_sysctl+0x10/0x10<br /> ? srso_return_thunk+0x5/0x5f<br /> ? __kvmalloc_node_noprof+0x345/0x870<br /> ? proc_sys_call_handler+0x250/0x480<br /> ? srso_return_thunk+0x5/0x5f<br /> proc_sys_call_handler+0x3a2/0x480<br /> ? __pfx_proc_sys_call_handler+0x10/0x10<br /> ? srso_return_thunk+0x5/0x5f<br /> ? selinux_file_permission+0x39f/0x500<br /> ? srso_return_thunk+0x5/0x5f<br /> ? lock_is_held_type+0x9e/0x120<br /> vfs_write+0x98e/0x1000<br /> ...<br /> <br /> <br /> With this fix applied on top of the same test setup, rerunning the<br /> reproducer with fail-nth=1 yields no corresponding Oops reports.