In the Linux kernel, the following vulnerability has been resolved: xdp: use flags field to disambiguate broadcast redirect When redirecting a packet using XDP, the bpf_redirect_map() helper will set up the redirect destination information in struct bpf_redirect_info (using the __bpf_xdp_redirect_map() helper function), and the xdp_do_redirect() function will read this information after the XDP program returns and pass the frame on to the right redirect destination. When using the BPF_F_BROADCAST flag to do multicast redirect to a whole map, __bpf_xdp_redirect_map() sets the 'map' pointer in struct bpf_redirect_info to point to the destination map to be broadcast. And xdp_do_redirect() reacts to the value of this map pointer to decide whether it's dealing with a broadcast or a single-value redirect. However, if the destination map is being destroyed before xdp_do_redirect() is called, the map pointer will be cleared out (by bpf_clear_redirect_map()) without waiting for any XDP programs to stop running. This causes xdp_do_redirect() to think that the redirect was to a single target, but the target pointer is also NULL (since broadcast redirects don't have a single target), so this causes a crash when a NULL pointer is passed to dev_map_enqueue(). To fix this, change xdp_do_redirect() to react directly to the presence of the BPF_F_BROADCAST flag in the 'flags' value in struct bpf_redirect_info to disambiguate between a single-target and a broadcast redirect. And only read the 'map' pointer if the broadcast flag is set, aborting if that has been cleared out in the meantime. This prevents the crash, while keeping the atomic (cmpxchg-based) clearing of the map pointer itself, and without adding any more checks in the non-broadcast fast path.
History

Wed, 11 Sep 2024 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 11 Sep 2024 13:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2024-05-30T15:29:26.353Z

Updated: 2024-11-05T09:28:25.105Z

Reserved: 2024-05-30T15:25:07.071Z

Link: CVE-2024-36937

cve-icon Vulnrichment

Updated: 2024-08-02T03:43:50.646Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2024-05-30T16:15:16.797

Modified: 2024-11-21T09:22:51.593

Link: CVE-2024-36937

cve-icon Redhat

Severity : Low

Publid Date: 2024-05-30T00:00:00Z

Links: CVE-2024-36937 - Bugzilla