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/quota/netlink.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 103 insertions(+) create mode 100644 fs/quota/netlink.c (limited to 'fs/quota/netlink.c') diff --git a/fs/quota/netlink.c b/fs/quota/netlink.c new file mode 100644 index 000000000..95acdae39 --- /dev/null +++ b/fs/quota/netlink.c @@ -0,0 +1,103 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include + +static const struct genl_multicast_group quota_mcgrps[] = { + { .name = "events", }, +}; + +/* Netlink family structure for quota */ +static struct genl_family quota_genl_family __ro_after_init = { + .module = THIS_MODULE, + .hdrsize = 0, + .name = "VFS_DQUOT", + .version = 1, + .maxattr = QUOTA_NL_A_MAX, + .mcgrps = quota_mcgrps, + .n_mcgrps = ARRAY_SIZE(quota_mcgrps), +}; + +/** + * quota_send_warning - Send warning to userspace about exceeded quota + * @qid: The kernel internal quota identifier. + * @dev: The device on which the fs is mounted (sb->s_dev) + * @warntype: The type of the warning: QUOTA_NL_... + * + * This can be used by filesystems (including those which don't use + * dquot) to send a message to userspace relating to quota limits. + * + */ + +void quota_send_warning(struct kqid qid, dev_t dev, + const char warntype) +{ + static atomic_t seq; + struct sk_buff *skb; + void *msg_head; + int ret; + int msg_size = 4 * nla_total_size(sizeof(u32)) + + 2 * nla_total_size_64bit(sizeof(u64)); + + /* We have to allocate using GFP_NOFS as we are called from a + * filesystem performing write and thus further recursion into + * the fs to free some data could cause deadlocks. */ + skb = genlmsg_new(msg_size, GFP_NOFS); + if (!skb) { + printk(KERN_ERR + "VFS: Not enough memory to send quota warning.\n"); + return; + } + msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq), + "a_genl_family, 0, QUOTA_NL_C_WARNING); + if (!msg_head) { + printk(KERN_ERR + "VFS: Cannot store netlink header in quota warning.\n"); + goto err_out; + } + ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type); + if (ret) + goto attr_err_out; + ret = nla_put_u64_64bit(skb, QUOTA_NL_A_EXCESS_ID, + from_kqid_munged(&init_user_ns, qid), + QUOTA_NL_A_PAD); + if (ret) + goto attr_err_out; + ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype); + if (ret) + goto attr_err_out; + ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev)); + if (ret) + goto attr_err_out; + ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev)); + if (ret) + goto attr_err_out; + ret = nla_put_u64_64bit(skb, QUOTA_NL_A_CAUSED_ID, + from_kuid_munged(&init_user_ns, current_uid()), + QUOTA_NL_A_PAD); + if (ret) + goto attr_err_out; + genlmsg_end(skb, msg_head); + + genlmsg_multicast("a_genl_family, skb, 0, 0, GFP_NOFS); + return; +attr_err_out: + printk(KERN_ERR "VFS: Not enough space to compose quota message!\n"); +err_out: + kfree_skb(skb); +} +EXPORT_SYMBOL(quota_send_warning); + +static int __init quota_init(void) +{ + if (genl_register_family("a_genl_family) != 0) + printk(KERN_ERR + "VFS: Failed to create quota netlink interface.\n"); + return 0; +}; +fs_initcall(quota_init); -- cgit v1.3.1