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/hpfs/dentry.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 fs/hpfs/dentry.c (limited to 'fs/hpfs/dentry.c') diff --git a/fs/hpfs/dentry.c b/fs/hpfs/dentry.c new file mode 100644 index 000000000..89a36fdc6 --- /dev/null +++ b/fs/hpfs/dentry.c @@ -0,0 +1,62 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/fs/hpfs/dentry.c + * + * Mikulas Patocka (mikulas@artax.karlin.mff.cuni.cz), 1998-1999 + * + * dcache operations + */ + +#include "hpfs_fn.h" + +/* + * Note: the dentry argument is the parent dentry. + */ + +static int hpfs_hash_dentry(const struct dentry *dentry, struct qstr *qstr) +{ + unsigned long hash; + int i; + unsigned l = qstr->len; + + if (l == 1) if (qstr->name[0]=='.') goto x; + if (l == 2) if (qstr->name[0]=='.' || qstr->name[1]=='.') goto x; + hpfs_adjust_length(qstr->name, &l); + /*if (hpfs_chk_name(qstr->name,&l))*/ + /*return -ENAMETOOLONG;*/ + /*return -ENOENT;*/ + x: + + hash = init_name_hash(dentry); + for (i = 0; i < l; i++) + hash = partial_name_hash(hpfs_upcase(hpfs_sb(dentry->d_sb)->sb_cp_table,qstr->name[i]), hash); + qstr->hash = end_name_hash(hash); + + return 0; +} + +static int hpfs_compare_dentry(const struct dentry *dentry, + unsigned int len, const char *str, const struct qstr *name) +{ + unsigned al = len; + unsigned bl = name->len; + + hpfs_adjust_length(str, &al); + /*hpfs_adjust_length(b->name, &bl);*/ + + /* + * 'str' is the nane of an already existing dentry, so the name + * must be valid. 'name' must be validated first. + */ + + if (hpfs_chk_name(name->name, &bl)) + return 1; + if (hpfs_compare_names(dentry->d_sb, str, al, name->name, bl, 0)) + return 1; + return 0; +} + +const struct dentry_operations hpfs_dentry_operations = { + .d_hash = hpfs_hash_dentry, + .d_compare = hpfs_compare_dentry, +}; -- cgit v1.3.1