7.8
CWE
416
Advisory Published
CVE Published
Updated

CVE-2023-52447: bpf: Defer the free of inner map when necessary

First published: Thu Feb 22 2024(Updated: )

In the Linux kernel, the following vulnerability has been resolved: bpf: Defer the free of inner map when necessary When updating or deleting an inner map in map array or map htab, the map may still be accessed by non-sleepable program or sleepable program. However bpf_map_fd_put_ptr() decreases the ref-counter of the inner map directly through bpf_map_put(), if the ref-counter is the last one (which is true for most cases), the inner map will be freed by ops->map_free() in a kworker. But for now, most .map_free() callbacks don't use synchronize_rcu() or its variants to wait for the elapse of a RCU grace period, so after the invocation of ops->map_free completes, the bpf program which is accessing the inner map may incur use-after-free problem. Fix the free of inner map by invoking bpf_map_free_deferred() after both one RCU grace period and one tasks trace RCU grace period if the inner map has been removed from the outer map before. The deferment is accomplished by using call_rcu() or call_rcu_tasks_trace() when releasing the last ref-counter of bpf map. The newly-added rcu_head field in bpf_map shares the same storage space with work field to reduce the size of bpf_map.

Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Affected SoftwareAffected VersionHow to fix
Linux Linux kernel>=5.9.0<5.10.214
Linux Linux kernel>=5.11<5.15.153
Linux Linux kernel>=5.16<6.1.75
Linux Linux kernel>=6.2<6.6.14
Linux Linux kernel>=6.7<6.7.2
debian/linux
5.10.223-1
5.10.226-1
6.1.115-1
6.1.119-1
6.11.10-1

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