From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- fs/smb/client/unc.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) create mode 100644 fs/smb/client/unc.c (limited to 'fs/smb/client/unc.c') diff --git a/fs/smb/client/unc.c b/fs/smb/client/unc.c new file mode 100644 index 000000000..f6fc5e343 --- /dev/null +++ b/fs/smb/client/unc.c @@ -0,0 +1,69 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2020, Microsoft Corporation. + * + * Author(s): Steve French + * Suresh Jayaraman + * Jeff Layton + */ + +#include +#include +#include +#include +#include "cifsglob.h" +#include "cifsproto.h" + +/* extract the host portion of the UNC string */ +char *extract_hostname(const char *unc) +{ + const char *src; + char *dst, *delim; + unsigned int len; + + /* skip double chars at beginning of string */ + /* BB: check validity of these bytes? */ + if (strlen(unc) < 3) + return ERR_PTR(-EINVAL); + for (src = unc; *src && *src == '\\'; src++) + ; + if (!*src) + return ERR_PTR(-EINVAL); + + /* delimiter between hostname and sharename is always '\\' now */ + delim = strchr(src, '\\'); + if (!delim) + return ERR_PTR(-EINVAL); + + len = delim - src; + dst = kmalloc((len + 1), GFP_KERNEL); + if (dst == NULL) + return ERR_PTR(-ENOMEM); + + memcpy(dst, src, len); + dst[len] = '\0'; + + return dst; +} + +char *extract_sharename(const char *unc) +{ + const char *src; + char *delim, *dst; + + /* skip double chars at the beginning */ + src = unc + 2; + + /* share name is always preceded by '\\' now */ + delim = strchr(src, '\\'); + if (!delim) + return ERR_PTR(-EINVAL); + delim++; + + /* caller has to free the memory */ + dst = kstrdup(delim, GFP_KERNEL); + if (!dst) + return ERR_PTR(-ENOMEM); + + return dst; +} -- cgit v1.3.1