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audit: ignore fcaps on umount

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Don't fetch fcaps when umount2 is called to avoid a process hang while
it waits for the missing resource to (possibly never) re-appear.

Note the comment above user_path_mountpoint_at():
 * A umount is a special case for path walking. We're not actually interested
 * in the inode in this situation, and ESTALE errors can be a problem.  We
 * simply want track down the dentry and vfsmount attached at the mountpoint
 * and avoid revalidating the last component.

This can happen on ceph, cifs, 9p, lustre, fuse (gluster) or NFS.

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

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
[PM: merge fuzz in audit_log_fcaps()]
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Richard Guy Briggs 2019-01-23 13:35:00 -05:00 committed by Paul Moore
parent 05c7a9cb27
commit 57d4657716
7 changed files with 29 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/namei.c
View File

@ -2720,7 +2720,7 @@ filename_mountpoint(int dfd, struct filename *name, struct path *path,
if (unlikely(error == -ESTALE))
error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path);
if (likely(!error))
audit_inode(name, path->dentry, 0);
audit_inode(name, path->dentry, flags & LOOKUP_NO_EVAL);
restore_nameidata();
putname(name);
return error;

2
fs/namespace.c
View File

@ -1640,6 +1640,8 @@ int ksys_umount(char __user *name, int flags)
if (!(flags & UMOUNT_NOFOLLOW))
lookup_flags |= LOOKUP_FOLLOW;
lookup_flags |= LOOKUP_NO_EVAL;
retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path);
if (retval)
goto out;

15
include/linux/audit.h
View File

@ -25,6 +25,7 @@
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/namei.h> /* LOOKUP_* */
#include <uapi/linux/audit.h>
#define AUDIT_INO_UNSET ((unsigned long)-1)
@ -248,6 +249,7 @@ extern void __audit_getname(struct filename *name);
#define AUDIT_INODE_PARENT 1 /* dentry represents the parent */
#define AUDIT_INODE_HIDDEN 2 /* audit record should be hidden */
#define AUDIT_INODE_NOEVAL 4 /* audit record incomplete */
extern void __audit_inode(struct filename *name, const struct dentry *dentry,
unsigned int flags);
extern void __audit_file(const struct file *);
@ -308,12 +310,15 @@ static inline void audit_getname(struct filename *name)
}
static inline void audit_inode(struct filename *name,
const struct dentry *dentry,
unsigned int parent) {
unsigned int flags) {
if (unlikely(!audit_dummy_context())) {
unsigned int flags = 0;
if (parent)
flags |= AUDIT_INODE_PARENT;
__audit_inode(name, dentry, flags);
unsigned int aflags = 0;
if (flags & LOOKUP_PARENT)
aflags |= AUDIT_INODE_PARENT;
if (flags & LOOKUP_NO_EVAL)
aflags |= AUDIT_INODE_NOEVAL;
__audit_inode(name, dentry, aflags);
}
}
static inline void audit_file(struct file *file)

3
include/linux/namei.h
View File

@ -24,6 +24,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
* - internal "there are more path components" flag
* - dentry cache is untrusted; force a real lookup
* - suppress terminal automount
* - skip revalidation
* - don't fetch xattrs on audit_inode
*/
#define LOOKUP_FOLLOW 0x0001
#define LOOKUP_DIRECTORY 0x0002
@ -33,6 +35,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
#define LOOKUP_REVAL 0x0020
#define LOOKUP_RCU 0x0040
#define LOOKUP_NO_REVAL 0x0080
#define LOOKUP_NO_EVAL 0x0100
/*
* Intent data

10
kernel/audit.c
View File

@ -2082,6 +2082,10 @@ void audit_log_cap(struct audit_buffer *ab, char *prefix, kernel_cap_t *cap)
static void audit_log_fcaps(struct audit_buffer *ab, struct audit_names *name)
{
if (name->fcap_ver == -1) {
audit_log_format(ab, " cap_fe=? cap_fver=? cap_fp=? cap_fi=?");
return;
}
audit_log_cap(ab, "cap_fp", &name->fcap.permitted);
audit_log_cap(ab, "cap_fi", &name->fcap.inheritable);
audit_log_format(ab, " cap_fe=%d cap_fver=%x cap_frootid=%d",
@ -2114,7 +2118,7 @@ static inline int audit_copy_fcaps(struct audit_names *name,
/* Copy inode data into an audit_names. */
void audit_copy_inode(struct audit_names *name, const struct dentry *dentry,
struct inode *inode)
struct inode *inode, unsigned int flags)
{
name->ino = inode->i_ino;
name->dev = inode->i_sb->s_dev;
@ -2123,6 +2127,10 @@ 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 (flags & AUDIT_INODE_NOEVAL) {
name->fcap_ver = -1;
return;
}
audit_copy_fcaps(name, dentry);
}

2
kernel/audit.h
View File

@ -215,7 +215,7 @@ extern void audit_log_session_info(struct audit_buffer *ab);
extern void audit_copy_inode(struct audit_names *name,
const struct dentry *dentry,
struct inode *inode);
struct inode *inode, unsigned int flags);
extern void audit_log_cap(struct audit_buffer *ab, char *prefix,
kernel_cap_t *cap);
extern void audit_log_name(struct audit_context *context,

6
kernel/auditsc.c
View File

@ -1856,7 +1856,7 @@ out:
n->type = AUDIT_TYPE_NORMAL;
}
handle_path(dentry);
audit_copy_inode(n, dentry, inode);
audit_copy_inode(n, dentry, inode, flags & AUDIT_INODE_NOEVAL);
}
void __audit_file(const struct file *file)
@ -1955,7 +1955,7 @@ void __audit_inode_child(struct inode *parent,
n = audit_alloc_name(context, AUDIT_TYPE_PARENT);
if (!n)
return;
audit_copy_inode(n, NULL, parent);
audit_copy_inode(n, NULL, parent, 0);
}
if (!found_child) {
@ -1974,7 +1974,7 @@ void __audit_inode_child(struct inode *parent,
}
if (inode)
audit_copy_inode(found_child, dentry, inode);
audit_copy_inode(found_child, dentry, inode, 0);
else
found_child->ino = AUDIT_INO_UNSET;
}