CVE-2024-56558

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> nfsd: make sure exp active before svc_export_show<br /> <br /> The function `e_show` was called with protection from RCU. This only<br /> ensures that `exp` will not be freed. Therefore, the reference count for<br /> `exp` can drop to zero, which will trigger a refcount use-after-free<br /> warning when `exp_get` is called. To resolve this issue, use<br /> `cache_get_rcu` to ensure that `exp` remains active.<br /> <br /> ------------[ cut here ]------------<br /> refcount_t: addition on 0; use-after-free.<br /> WARNING: CPU: 3 PID: 819 at lib/refcount.c:25<br /> refcount_warn_saturate+0xb1/0x120<br /> CPU: 3 UID: 0 PID: 819 Comm: cat Not tainted 6.12.0-rc3+ #1<br /> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS<br /> 1.16.1-2.fc37 04/01/2014<br /> RIP: 0010:refcount_warn_saturate+0xb1/0x120<br /> ...<br /> Call Trace:<br /> <br /> e_show+0x20b/0x230 [nfsd]<br /> seq_read_iter+0x589/0x770<br /> seq_read+0x1e5/0x270<br /> vfs_read+0x125/0x530<br /> ksys_read+0xc1/0x160<br /> do_syscall_64+0x5f/0x170<br /> entry_SYSCALL_64_after_hwframe+0x76/0x7e