CVE-2022-50654

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix panic due to wrong pageattr of im->image

In the scenario where livepatch and kretfunc coexist, the pageattr of im->image is rox after archpreparebpftrampoline in bpftrampolineupdate, and then modifyfentry or registerfentry returns -EAGAIN from bpftrampftraceopsfunc, the BPFTRAMPFORIGSTACK flag will be configured, and archpreparebpftrampoline will be re-executed.

At this time, because the pageattr of im->image is rox, archpreparebpf_trampoline will read and write im->image, which causes a fault. as follows:

insmod livepatch-sample.ko # samples/livepatch/livepatch-sample.c bpftrace -e 'kretfunc:cmdlineprocshow {}'

BUG: unable to handle page fault for address: ffffffffa0206000 PGD 322d067 P4D 322d067 PUD 322e063 PMD 1297e067 PTE d428061 Oops: 0003 [#1] PREEMPT SMP PTI CPU: 2 PID: 270 Comm: bpftrace Tainted: G E K 6.1.0 #5 RIP: 0010:archpreparebpftrampoline+0xed/0x8c0 RSP: 0018:ffffc90001083ad8 EFLAGS: 00010202 RAX: ffffffffa0206000 RBX: 0000000000000020 RCX: 0000000000000000 RDX: ffffffffa0206001 RSI: ffffffffa0206000 RDI: 0000000000000030 RBP: ffffc90001083b70 R08: 0000000000000066 R09: ffff88800f51b400 R10: 000000002e72c6e5 R11: 00000000d0a15080 R12: ffff8880110a68c8 R13: 0000000000000000 R14: ffff88800f51b400 R15: ffffffff814fec10 FS: 00007f87bc0dc780(0000) GS:ffff88803e600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffa0206000 CR3: 0000000010b70000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> bpftrampoline_update+0x25a/0x6b0 __bpftrampolinelinkprog+0x101/0x240 bpftrampolinelinkprog+0x2d/0x50 bpftracingprogattach+0x24c/0x530 bpfrawtplink_attach+0x73/0x1d0 __sys_bpf+0x100e/0x2570 __x64sysbpf+0x1c/0x30 dosyscall64+0x5b/0x80 entrySYSCALL64afterhwframe+0x63/0xcd

With this patch, when modifyfentry or registerfentry returns -EAGAIN from bpftrampftraceopsfunc, the pageattr of im->image will be reset to nx+rw.