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audit: more filter PATH records keyed on filesystem magic

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Like commit 42d5e37654 ("audit: filter PATH records keyed on
filesystem magic") that addresses
https://github.com/linux-audit/audit-kernel/issues/8

Any user or remote filesystem could become unavailable and effectively
block on a forced unmount.

    -a always,exit -S umount2 -F key=umount2

Provide a method to ignore these user and remote filesystems to prevent
them from being impossible to unmount.

Extend the "AUDIT_FILTER_FS" filter that uses the field type
AUDIT_FSTYPE keying off the filesystem 4-octet hexadecimal magic
identifier to filter specific filesystems to cover audit_inode() to address
this blockage.

An example rule would look like:
    -a never,filesystem -F fstype=0x517B -F key=ignore_smb
    -a never,filesystem -F fstype=0x6969 -F key=ignore_nfs

Arguably the better way to address this issue is to disable auditing
processes that touch removable filesystems.

Note: refactor __audit_inode_child() to remove two levels of if
indentation.

Please see the github issue tracker
https://github.com/linux-audit/audit-kernel/issues/100

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Richard Guy Briggs 2019-01-23 13:34:59 -05:00 committed by Paul Moore
parent 2fec30e245
commit a252f56a3c
1 changed files with 27 additions and 8 deletions
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35
kernel/auditsc.c
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@ -1766,10 +1766,31 @@ void __audit_inode(struct filename *name, const struct dentry *dentry,
struct inode *inode = d_backing_inode(dentry);
struct audit_names *n;
bool parent = flags & AUDIT_INODE_PARENT;
struct audit_entry *e;
struct list_head *list = &audit_filter_list[AUDIT_FILTER_FS];
int i;
if (!context->in_syscall)
return;
rcu_read_lock();
if (!list_empty(list)) {
list_for_each_entry_rcu(e, list, list) {
for (i = 0; i < e->rule.field_count; i++) {
struct audit_field *f = &e->rule.fields[i];
if (f->type == AUDIT_FSTYPE
&& audit_comparator(inode->i_sb->s_magic,
f->op, f->val)
&& e->rule.action == AUDIT_NEVER) {
rcu_read_unlock();
return;
}
}
}
}
rcu_read_unlock();
if (!name)
goto out_alloc;
@ -1878,14 +1899,12 @@ void __audit_inode_child(struct inode *parent,
for (i = 0; i < e->rule.field_count; i++) {
struct audit_field *f = &e->rule.fields[i];
if (f->type == AUDIT_FSTYPE) {
if (audit_comparator(parent->i_sb->s_magic,
f->op, f->val)) {
if (e->rule.action == AUDIT_NEVER) {
rcu_read_unlock();
return;
}
}
if (f->type == AUDIT_FSTYPE
&& audit_comparator(parent->i_sb->s_magic,
f->op, f->val)
&& e->rule.action == AUDIT_NEVER) {
rcu_read_unlock();
return;
}
}
}