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 --- drivers/md/dm-verity-loadpin.c | 86 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 86 insertions(+) create mode 100644 drivers/md/dm-verity-loadpin.c (limited to 'drivers/md/dm-verity-loadpin.c') diff --git a/drivers/md/dm-verity-loadpin.c b/drivers/md/dm-verity-loadpin.c new file mode 100644 index 000000000..9a64f575a --- /dev/null +++ b/drivers/md/dm-verity-loadpin.c @@ -0,0 +1,86 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include +#include +#include + +#include "dm.h" +#include "dm-core.h" +#include "dm-verity.h" + +#define DM_MSG_PREFIX "verity-loadpin" + +LIST_HEAD(dm_verity_loadpin_trusted_root_digests); + +static bool is_trusted_verity_target(struct dm_target *ti) +{ + int verity_mode; + u8 *root_digest; + unsigned int digest_size; + struct dm_verity_loadpin_trusted_root_digest *trd; + bool trusted = false; + + if (!dm_is_verity_target(ti)) + return false; + + verity_mode = dm_verity_get_mode(ti); + + if ((verity_mode != DM_VERITY_MODE_EIO) && + (verity_mode != DM_VERITY_MODE_RESTART) && + (verity_mode != DM_VERITY_MODE_PANIC)) + return false; + + if (dm_verity_get_root_digest(ti, &root_digest, &digest_size)) + return false; + + list_for_each_entry(trd, &dm_verity_loadpin_trusted_root_digests, node) { + if ((trd->len == digest_size) && + !memcmp(trd->data, root_digest, digest_size)) { + trusted = true; + break; + } + } + + kfree(root_digest); + + return trusted; +} + +/* + * Determines whether the file system of a superblock is located on + * a verity device that is trusted by LoadPin. + */ +bool dm_verity_loadpin_is_bdev_trusted(struct block_device *bdev) +{ + struct mapped_device *md; + struct dm_table *table; + struct dm_target *ti; + int srcu_idx; + bool trusted = false; + + if (bdev == NULL) + return false; + + if (list_empty(&dm_verity_loadpin_trusted_root_digests)) + return false; + + md = dm_get_md(bdev->bd_dev); + if (!md) + return false; + + table = dm_get_live_table(md, &srcu_idx); + + if (!table || table->num_targets != 1) + goto out; + + ti = dm_table_get_target(table, 0); + + if (is_trusted_verity_target(ti)) + trusted = true; + +out: + dm_put_live_table(md, srcu_idx); + dm_put(md); + + return trusted; +} -- cgit v1.3.1