perf/core: Fix a refcount leak in attach_perf_ctx_data()

Overview

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

perf/core: Fix a refcount leak in attach_perf_ctx_data()

The attach_perf_ctx_data() can race on global and !global cases. The global case is protected by global_ctx_data_rwsem and shares a single reference count using perf_ctx_data.global field.

But when it races with !global case, it may miss to set the global field and result in a reference count leak.

CPU1 CPU2

attach_task_ctx_data(.global=1) attach_task_ctx_data(.global=0) cd1 = alloc_perf_ctx_data(); cd2 = alloc_perf_ctx_data(); // { .global = 0, .refcount = 1 };

                                     try_cmpxchg(); // success,
                                     // task->perf_ctx_data = cd2

try_cmpxhg(); // fail; old = cd2 refcount_inc_not_zero(&old->refcount); // success // old.refcount = 2 free_perf_ctx_data(cd1);

Then later detach_global_ctx_data() will see the data but it's not marked as global, so it won't call detach_task_ctx_data().

Affected

• Linux >= 506e64e710ff9573fd2b86686528762b7901b5e4 < 23250517cd475367653f1e99396967f54c6f1b7c
• Linux >= 506e64e710ff9573fd2b86686528762b7901b5e4 < 5286d4eb5cd7e10d7d93c3cc596e18bc8ad80f72
• Linux >= 506e64e710ff9573fd2b86686528762b7901b5e4 < cca4980630b3c7a85f53cb43c6018184ce5d4e37
• Linux 6.15

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.