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| author | Jann Horn <jannh@google.com> | 2018-09-13 18:12:09 +0200 |
|---|---|---|
| committer | John Johansen <john.johansen@canonical.com> | 2018-09-13 09:44:56 -0700 |
| commit | 1f8266ff58840d698a1e96d2274189de1bdf7969 (patch) | |
| tree | 22ec503efa895edcbc8a0bdd465d4206cad19311 /security | |
| parent | 5f997580e8b12b9f585e34cc16304925d26ce49e (diff) | |
| download | lwn-1f8266ff58840d698a1e96d2274189de1bdf7969.tar.gz lwn-1f8266ff58840d698a1e96d2274189de1bdf7969.zip | |
apparmor: don't try to replace stale label in ptrace access check
As a comment above begin_current_label_crit_section() explains,
begin_current_label_crit_section() must run in sleepable context because
when label_is_stale() is true, aa_replace_current_label() runs, which uses
prepare_creds(), which can sleep.
Until now, the ptrace access check (which runs with a task lock held)
violated this rule.
Also add a might_sleep() assertion to begin_current_label_crit_section(),
because asserts are less likely to be ignored than comments.
Fixes: b2d09ae449ced ("apparmor: move ptrace checks to using labels")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Diffstat (limited to 'security')
| -rw-r--r-- | security/apparmor/include/cred.h | 2 | ||||
| -rw-r--r-- | security/apparmor/lsm.c | 4 |
2 files changed, 4 insertions, 2 deletions
diff --git a/security/apparmor/include/cred.h b/security/apparmor/include/cred.h index e287b7d0d4be..265ae6641a06 100644 --- a/security/apparmor/include/cred.h +++ b/security/apparmor/include/cred.h @@ -151,6 +151,8 @@ static inline struct aa_label *begin_current_label_crit_section(void) { struct aa_label *label = aa_current_raw_label(); + might_sleep(); + if (label_is_stale(label)) { label = aa_get_newest_label(label); if (aa_replace_current_label(label) == 0) diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c index 74f17376202b..f09fea0b4db7 100644 --- a/security/apparmor/lsm.c +++ b/security/apparmor/lsm.c @@ -114,13 +114,13 @@ static int apparmor_ptrace_access_check(struct task_struct *child, struct aa_label *tracer, *tracee; int error; - tracer = begin_current_label_crit_section(); + tracer = __begin_current_label_crit_section(); tracee = aa_get_task_label(child); error = aa_may_ptrace(tracer, tracee, (mode & PTRACE_MODE_READ) ? AA_PTRACE_READ : AA_PTRACE_TRACE); aa_put_label(tracee); - end_current_label_crit_section(tracer); + __end_current_label_crit_section(tracer); return error; } |