Audit link denied events were being unexpectedly produced in a disjoint
way when audit was disabled, and when they were expected, there were
duplicate PATH records.  This patchset addresses both issues for
symlinks and hardlinks.

This was introduced with
        commit b24a30a7305418ff138ff51776fc555ec57c011a
        ("audit: fix event coverage of AUDIT_ANOM_LINK")
        commit a51d9eaa41866ab6b4b6ecad7b621f8b66ece0dc
        ("fs: add link restriction audit reporting")

Here are the resulting events:

symlink:
type=PROCTITLE msg=audit(03/12/2018 02:21:49.578:310) : proctitle=ls 
./my-passwd 
type=PATH msg=audit(03/12/2018 02:21:49.578:310) : item=1 name=/tmp/ 
inode=13529 dev=00:27 mode=dir,sticky,777 ouid=root ogid=root rdev=00:00 
obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none cap_fi=none cap_fe=0 
cap_fver=0 
type=PATH msg=audit(03/12/2018 02:21:49.578:310) : item=0 name=./my-passwd 
inode=17090 dev=00:27 mode=link,777 ouid=rgb ogid=rgb rdev=00:00 
obj=unconfined_u:object_r:user_tmp_t:s0 nametype=NORMAL cap_fp=none cap_fi=none 
cap_fe=0 cap_fver=0 
type=CWD msg=audit(03/12/2018 02:21:49.578:310) : cwd=/tmp 
type=SYSCALL msg=audit(03/12/2018 02:21:49.578:310) : arch=x86_64 syscall=stat 
success=no exit=EACCES(Permission denied) a0=0x7ffd79950dda a1=0x563f658a03c8 
a2=0x563f658a03c8 a3=0x79950d00 items=2 ppid=552 pid=629 auid=root uid=root 
gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root 
tty=ttyS0 ses=1 comm=ls exe=/usr/bin/ls 
subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) 
type=ANOM_LINK msg=audit(03/12/2018 02:21:49.578:310) : op=follow_link ppid=552 
pid=629 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=root 
sgid=root fsgid=root tty=ttyS0 ses=1 comm=ls exe=/usr/bin/ls 
subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no 
----
hardlink:
type=PROCTITLE msg=audit(03/12/2018 02:24:39.813:314) : proctitle=ln test 
test-ln 
type=PATH msg=audit(03/12/2018 02:24:39.813:314) : item=1 name=/tmp inode=13529 
dev=00:27 mode=dir,sticky,777 ouid=root ogid=root rdev=00:00 
obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none cap_fi=none cap_fe=0 
cap_fver=0 
type=PATH msg=audit(03/12/2018 02:24:39.813:314) : item=0 name=test inode=18112 
dev=00:27 mode=file,700 ouid=root ogid=root rdev=00:00 
obj=unconfined_u:object_r:user_tmp_t:s0 nametype=NORMAL cap_fp=none cap_fi=none 
cap_fe=0 cap_fver=0 
type=CWD msg=audit(03/12/2018 02:24:39.813:314) : cwd=/tmp 
type=SYSCALL msg=audit(03/12/2018 02:24:39.813:314) : arch=x86_64 
syscall=linkat success=no exit=EPERM(Operation not permitted) a0=0xffffff9c 
a1=0x7ffccba77629 a2=0xffffff9c a3=0x7ffccba7762e items=2 ppid=605 pid=638 
auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb egid=rgb sgid=rgb 
fsgid=rgb tty=pts0 ses=4 comm=ln exe=/usr/bin/ln 
subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) 
type=ANOM_LINK msg=audit(03/12/2018 02:24:39.813:314) : op=linkat ppid=605 
pid=638 auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb egid=rgb sgid=rgb 
fsgid=rgb tty=pts0 ses=4 comm=ln exe=/usr/bin/ln 
subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no 

See: https://github.com/linux-audit/audit-kernel/issues/21
See also: https://github.com/linux-audit/audit-kernel/issues/51

Richard Guy Briggs (4):
  audit: make ANOM_LINK obey audit_enabled and audit_dummy_context
  audit: link denied should not directly generate PATH record
  audit: add refused symlink to audit_names
  audit: add parent of refused symlink to audit_names

 fs/namei.c            |  5 +++--
 include/linux/audit.h |  9 +++++----
 kernel/audit.c        | 43 ++++++++++++++++++++++++++++++++-----------
 3 files changed, 40 insertions(+), 17 deletions(-)

-- 
1.8.3.1

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