Re: [PATCH ghak8 ALT4 V4 1/3] audit: show partial pathname for entries with anonymous parents

On Monday, February 12, 2018 12:02:21 AM EST Richard Guy Briggs wrote: > Tracefs or debugfs were causing hundreds to thousands of null PATH > records to be associated with the init_module and finit_module SYSCALL > records on a few modules when the following rule was in place for > startup: > -a always,exit -F arch=x86_64 -S init_module -F key=mod-load > > This happens because the parent inode is not found in the task's > audit_names list and hence treats it as anonymous. This gives us no > information other than a numerical device number for a device that may > no longer be visible upon log inspeciton, and an inode number. > > Fill in the partial known pathname from the filesystem mount point to > the leaf node on previously null PATH records from entries that have an > anonymous parent from the child dentry using dentry_path_raw(). > > Make the dentry argument of __audit_inode_child() non-const so that we > can take a reference to it in the case of an anonymous parent with > dget() and dget_parent() to be able to later print a partial path from > the host filesystem rather than null. > > Since all we are given is an inode of the parent and the dentry of the > child, finding the path from the mount point to the root of the > filesystem is more challenging that would involve searching all > vfsmounts from "/" until a matching dentry is found for that > filesystem's root dentry. Even if one is found, there may be more than > one mount point. At this point the gain seems marginal since > knowing the filesystem type and path are a significant help in tracking > down the source of the PATH records and being able to address them. > > Sample output: > type=PROCTITLE msg=audit(1488317694.446:143): > proctitle=2F7362696E2F6D6F6470726F6265002D71002D2D006E66737634 type=PATH > msg=audit(1488317694.446:143): item=797 > name=events/nfs4/nfs4_setclientid/format inode=15969 dev=00:09 > mode=0100444 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 > nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 > cap_fver=0 type=PATH msg=audit(1488317694.446:143): item=796 > name=events/nfs4/nfs4_setclientid inode=15964 dev=00:09 mode=040755 ouid=0 > ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=PARENT > cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 ... > type=PATH msg=audit(1488317694.446:143): item=1 name=events/nfs4 > inode=15571 dev=00:09 mode=040755 ouid=0 ogid=0 rdev=00:00 > obj=system_u:object_r:tracefs_t:s0 nametype=CREATE cap_fp=0000000000000000 > cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=PATH > msg=audit(1488317694.446:143): item=0 name=events inode=119 dev=00:09 > mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 > nametype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 > cap_fver=0 type=KERN_MODULE msg=audit(1488317694.446:143): name="nfsv4" > type=SYSCALL msg=audit(1488317694.446:143): arch=c000003e syscall=313 > success=yes exit=0 a0=1 a1=55d5a35ce106 a2=0 a3=1 items=798 ppid=6 pid=528 > auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 > tty=(none) ses=4294967295 comm="modprobe" exe="/usr/bin/kmod" > subj=system_u:system_r:insmod_t:s0 key="mod-load" Thanks for the samples, but the event above fails the ausearch-test test suite. The "name" field in the PATH record is not properly escaped.

-Steve > See: https://github.com/linux-audit/audit-kernel/issues/8 > Test case: https://github.com/linux-audit/audit-testsuite/issues/42 > > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > > --- > v4: > fix fullpath memleak > switch from log_format() to audit_log_untrustedstring() > remove leading / from pathname relative to unknown mount point > > v3: > fix audit_buffer leak and dname error allocation leak audit_log_name > only put audit_name->dentry if it is being replaced > > v2: > deconstify struct dentry* > add hex prefix to fstype > --- > include/linux/audit.h | 8 ++++---- > kernel/audit.c | 28 +++++++++++++++++++++++++++- > kernel/audit.h | 1 + > kernel/auditsc.c | 8 +++++++- > 4 files changed, 39 insertions(+), 6 deletions(-) > > diff --git a/include/linux/audit.h b/include/linux/audit.h > index af410d9..2020f1d 100644 > --- a/include/linux/audit.h > +++ b/include/linux/audit.h > @@ -232,7 +232,7 @@ extern void __audit_inode(struct filename *name, const > struct dentry *dentry, unsigned int flags); > extern void __audit_file(const struct file *); > extern void __audit_inode_child(struct inode *parent, > - const struct dentry *dentry, > + struct dentry *dentry, > const unsigned char type); > extern void __audit_seccomp(unsigned long syscall, long signr, int code); > extern void __audit_ptrace(struct task_struct *t); > @@ -297,7 +297,7 @@ static inline void audit_inode_parent_hidden(struct > filename *name, AUDIT_INODE_PARENT | AUDIT_INODE_HIDDEN); > } > static inline void audit_inode_child(struct inode *parent, > - const struct dentry *dentry, > + struct dentry *dentry, > const unsigned char type) { > if (unlikely(!audit_dummy_context())) > __audit_inode_child(parent, dentry, type); > @@ -481,7 +481,7 @@ static inline void __audit_inode(struct filename *name, > unsigned int flags) > { } > static inline void __audit_inode_child(struct inode *parent, > - const struct dentry *dentry, > + struct dentry *dentry, > const unsigned char type) > { } > static inline void audit_inode(struct filename *name, > @@ -495,7 +495,7 @@ static inline void audit_inode_parent_hidden(struct > filename *name, const struct dentry *dentry) > { } > static inline void audit_inode_child(struct inode *parent, > - const struct dentry *dentry, > + struct dentry *dentry, > const unsigned char type) > { } > static inline void audit_core_dumps(long signr) > diff --git a/kernel/audit.c b/kernel/audit.c > index 227db99..0c8d5a8 100644 > --- a/kernel/audit.c > +++ b/kernel/audit.c > @@ -72,6 +72,7 @@ > #include <linux/freezer.h> > #include <linux/pid_namespace.h> > #include <net/netns/generic.h> > +#include <linux/dcache.h> > > #include "audit.h" > > @@ -2056,6 +2057,10 @@ void audit_copy_inode(struct audit_names *name, > const struct dentry *dentry, name->gid = inode->i_gid; > name->rdev = inode->i_rdev; > security_inode_getsecid(inode, &name->osid); > + if (name->dentry) { > + dput(name->dentry); > + name->dentry = NULL; > + } > audit_copy_fcaps(name, dentry); > } > > @@ -2097,8 +2102,29 @@ void audit_log_name(struct audit_context *context, > struct audit_names *n, audit_log_n_untrustedstring(ab, n->name->name, > n->name_len); > } > - } else > + } else if (n->dentry) { > + char *fullpath; > + const char *fullpathp = NULL; > + > + fullpath = kmalloc(PATH_MAX, GFP_KERNEL); > + if (fullpath) { > + fullpathp = dentry_path_raw(n->dentry, fullpath, PATH_MAX); > + if (IS_ERR(fullpathp)) { > + fullpathp = NULL; > + } else { > + while (*fullpathp == '/') > + fullpathp++; > + if (*fullpathp == 0) > + fullpathp = NULL; > + } > + } > + audit_log_format(ab, " name="); > + audit_log_untrustedstring(ab, fullpathp ?: "?"); > + if (fullpath) > + kfree(fullpath); > + } else { > audit_log_format(ab, " name=(null)"); > + } > > if (n->ino != AUDIT_INO_UNSET) > audit_log_format(ab, " inode=%lu" > diff --git a/kernel/audit.h b/kernel/audit.h > index af5bc59..81f6865 100644 > --- a/kernel/audit.h > +++ b/kernel/audit.h > @@ -85,6 +85,7 @@ struct audit_names { > > unsigned long ino; > dev_t dev; > + struct dentry *dentry; > umode_t mode; > kuid_t uid; > kgid_t gid; > diff --git a/kernel/auditsc.c b/kernel/auditsc.c > index e80459f..b73ede0 100644 > --- a/kernel/auditsc.c > +++ b/kernel/auditsc.c > @@ -75,6 +75,7 @@ > #include <linux/uaccess.h> > #include <linux/fsnotify_backend.h> > #include <uapi/linux/limits.h> > +#include <linux/dcache.h> > > #include "audit.h" > > @@ -882,6 +883,8 @@ static inline void audit_free_names(struct > audit_context *context) list_del(&n->list); > if (n->name) > putname(n->name); > + if (n->dentry) > + dput(n->dentry); > if (n->should_free) > kfree(n); > } > @@ -1862,7 +1865,7 @@ void __audit_file(const struct file *file) > * unsuccessful attempts. > */ > void __audit_inode_child(struct inode *parent, > - const struct dentry *dentry, > + struct dentry *dentry, > const unsigned char type) > { > struct audit_context *context = current->audit_context; > @@ -1941,6 +1944,7 @@ void __audit_inode_child(struct inode *parent, > if (!n) > return; > audit_copy_inode(n, NULL, parent); > + n->dentry = dget_parent(dentry); > } > > if (!found_child) { > @@ -1962,6 +1966,8 @@ void __audit_inode_child(struct inode *parent, > audit_copy_inode(found_child, dentry, inode); > else > found_child->ino = AUDIT_INO_UNSET; > + if (!found_parent) > + found_child->dentry = dget(dentry); > } > EXPORT_SYMBOL_GPL(__audit_inode_child);