kernel/audit_tree.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
kill_rules() removes mixed AUDIT_DIR and AUDIT_EXE rules when an audit
tree is pruned. It drops entry->rule.exe before removing the rule from
the RCU-visible filter lists.
After a rule has been installed with AUDIT_ADD_RULE, which requires
CAP_AUDIT_CONTROL, removing or moving the watched directory can race
with another task that is still evaluating the rule. In that case,
fsnotify can free the executable mark before the reader reaches
audit_mark_compare(), causing a use-after-free.
KASAN reports:
BUG: KASAN: slab-use-after-free in audit_mark_compare+0x8d/0xa0
Remove the rule from the RCU-visible filter lists first, wait for a grace
period, and only then drop the executable mark. audit_del_rule() already
uses this ordering.
Fixes: 34d99af52ad4 ("audit: implement audit by executable")
Assisted-by: Codex:gpt-5
Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
---
kernel/audit_tree.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 1ed19b7..864a58b 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -553,11 +553,12 @@ static void kill_rules(struct audit_context *context, struct audit_tree *tree)
if (rule->tree) {
/* not a half-baked one */
audit_tree_log_remove_rule(context, rule);
- if (entry->rule.exe)
- audit_remove_mark(entry->rule.exe);
rule->tree = NULL;
list_del_rcu(&entry->list);
list_del(&entry->rule.list);
+ synchronize_rcu();
+ if (entry->rule.exe)
+ audit_remove_mark(entry->rule.exe);
call_rcu(&entry->rcu, audit_free_rule_rcu);
}
}
--
2.47.3
On Mon, Sep 21, 2026 at 5:07 PM Jérémy Jean
<Jeremy.Jean@oss.cyber.gouv.fr> wrote:
>
> kill_rules() removes mixed AUDIT_DIR and AUDIT_EXE rules when an audit
> tree is pruned. It drops entry->rule.exe before removing the rule from
> the RCU-visible filter lists.
>
> After a rule has been installed with AUDIT_ADD_RULE, which requires
> CAP_AUDIT_CONTROL, removing or moving the watched directory can race
> with another task that is still evaluating the rule. In that case,
> fsnotify can free the executable mark before the reader reaches
> audit_mark_compare(), causing a use-after-free.
>
> KASAN reports:
>
> BUG: KASAN: slab-use-after-free in audit_mark_compare+0x8d/0xa0
>
> Remove the rule from the RCU-visible filter lists first, wait for a grace
> period, and only then drop the executable mark. audit_del_rule() already
> uses this ordering.
>
> Fixes: 34d99af52ad4 ("audit: implement audit by executable")
> Assisted-by: Codex:gpt-5
> Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
> ---
> kernel/audit_tree.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> index 1ed19b7..864a58b 100644
> --- a/kernel/audit_tree.c
> +++ b/kernel/audit_tree.c
> @@ -553,11 +553,12 @@ static void kill_rules(struct audit_context *context, struct audit_tree *tree)
> if (rule->tree) {
> /* not a half-baked one */
> audit_tree_log_remove_rule(context, rule);
> - if (entry->rule.exe)
> - audit_remove_mark(entry->rule.exe);
> rule->tree = NULL;
> list_del_rcu(&entry->list);
> list_del(&entry->rule.list);
> + synchronize_rcu();
> + if (entry->rule.exe)
> + audit_remove_mark(entry->rule.exe);
> call_rcu(&entry->rcu, audit_free_rule_rcu);
> }
> }
> --
> 2.47.3
>
>
Hi Jérémy,
Thanks for troubleshooting and fixing this bug.
sashiko's review makes sense, though: synchronize_rcu() inside the
loop waits a full grace period per rule, and kill_rules() runs with
audit_filter_mutex held, so a tree with many rules stalls other audit
config operations. Below is an untested suggestion to use a single
grace period instead.
diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 1ed19b775912..5a3d7c7ba5ce 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -549,18 +549,30 @@ static void kill_rules(struct audit_context
*context, struct audit_tree *tree)
list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
entry = container_of(rule, struct audit_entry, rule);
- list_del_init(&rule->rlist);
if (rule->tree) {
/* not a half-baked one */
audit_tree_log_remove_rule(context, rule);
- if (entry->rule.exe)
- audit_remove_mark(entry->rule.exe);
rule->tree = NULL;
list_del_rcu(&entry->list);
list_del(&entry->rule.list);
- call_rcu(&entry->rcu, audit_free_rule_rcu);
+ } else {
+ list_del_init(&rule->rlist);
}
}
+
+ if (list_empty(&tree->rules))
+ return;
+
+ synchronize_rcu();
+
+ list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
+ entry = container_of(rule, struct audit_entry, rule);
+
+ list_del_init(&rule->rlist);
+ if (entry->rule.exe)
+ audit_remove_mark(entry->rule.exe);
+ call_rcu(&entry->rcu, audit_free_rule_rcu);
+ }
}
/*
--Ricardo
On 2026-09-22 13:26, Ricardo Robaina wrote:
> On Mon, Sep 21, 2026 at 5:07 PM Jérémy Jean
> <Jeremy.Jean@oss.cyber.gouv.fr> wrote:
>>
>> kill_rules() removes mixed AUDIT_DIR and AUDIT_EXE rules when an audit
>> tree is pruned. It drops entry->rule.exe before removing the rule from
>> the RCU-visible filter lists.
>>
>> After a rule has been installed with AUDIT_ADD_RULE, which requires
>> CAP_AUDIT_CONTROL, removing or moving the watched directory can race
>> with another task that is still evaluating the rule. In that case,
>> fsnotify can free the executable mark before the reader reaches
>> audit_mark_compare(), causing a use-after-free.
>>
>> KASAN reports:
>>
>> BUG: KASAN: slab-use-after-free in audit_mark_compare+0x8d/0xa0
>>
>> Remove the rule from the RCU-visible filter lists first, wait for a
>> grace
>> period, and only then drop the executable mark. audit_del_rule()
>> already
>> uses this ordering.
>>
>> Fixes: 34d99af52ad4 ("audit: implement audit by executable")
>> Assisted-by: Codex:gpt-5
>> Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
>> ---
>> kernel/audit_tree.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
>> index 1ed19b7..864a58b 100644
>> --- a/kernel/audit_tree.c
>> +++ b/kernel/audit_tree.c
>> @@ -553,11 +553,12 @@ static void kill_rules(struct audit_context
>> *context, struct audit_tree *tree)
>> if (rule->tree) {
>> /* not a half-baked one */
>> audit_tree_log_remove_rule(context, rule);
>> - if (entry->rule.exe)
>> - audit_remove_mark(entry->rule.exe);
>> rule->tree = NULL;
>> list_del_rcu(&entry->list);
>> list_del(&entry->rule.list);
>> + synchronize_rcu();
>> + if (entry->rule.exe)
>> + audit_remove_mark(entry->rule.exe);
>> call_rcu(&entry->rcu, audit_free_rule_rcu);
>> }
>> }
>> --
>> 2.47.3
>>
>>
>
> Hi Jérémy,
>
> Thanks for troubleshooting and fixing this bug.
>
> sashiko's review makes sense, though: synchronize_rcu() inside the
> loop waits a full grace period per rule, and kill_rules() runs with
> audit_filter_mutex held, so a tree with many rules stalls other audit
> config operations. Below is an untested suggestion to use a single
> grace period instead.
>
> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> index 1ed19b775912..5a3d7c7ba5ce 100644
> --- a/kernel/audit_tree.c
> +++ b/kernel/audit_tree.c
> @@ -549,18 +549,30 @@ static void kill_rules(struct audit_context
> *context, struct audit_tree *tree)
> list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
> entry = container_of(rule, struct audit_entry, rule);
>
> - list_del_init(&rule->rlist);
> if (rule->tree) {
> /* not a half-baked one */
> audit_tree_log_remove_rule(context, rule);
> - if (entry->rule.exe)
> - audit_remove_mark(entry->rule.exe);
> rule->tree = NULL;
> list_del_rcu(&entry->list);
> list_del(&entry->rule.list);
> - call_rcu(&entry->rcu, audit_free_rule_rcu);
> + } else {
> + list_del_init(&rule->rlist);
> }
> }
> +
> + if (list_empty(&tree->rules))
> + return;
> +
> + synchronize_rcu();
> +
> + list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
> + entry = container_of(rule, struct audit_entry, rule);
> +
> + list_del_init(&rule->rlist);
> + if (entry->rule.exe)
> + audit_remove_mark(entry->rule.exe);
> + call_rcu(&entry->rcu, audit_free_rule_rcu);
> + }
> }
>
> /*
Hello Ricardo,
Many thanks for your nice and constructive answer.
Indeed, sashiko's review makes sense and your suggested v2 is a good
fix.
I have replayed my reproducer to ensure that it indeeds fix the reported
bug.
However, I wonder whether the wait should still happen in the case where
all removed rules have rule->exe == NULL. Doesn't call_rcu() already
free (kernel/auditfilter.c:96)? If yes, could we skip synchronize_rcu()
in
that case? If this question is valid, how about this fix based on yours,
which
simply adds a bool to detect whether synchronize_rcu() should be called.
If you think this addition is good, I can send a v2 with that.
diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 1ed19b775912..e2cd27b17590 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -545,22 +545,38 @@ static void kill_rules(struct audit_context
*context, struct audit_tree *tree)
{
struct audit_krule *rule, *next;
struct audit_entry *entry;
+ bool need_sync = false;
list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
entry = container_of(rule, struct audit_entry, rule);
- list_del_init(&rule->rlist);
if (rule->tree) {
/* not a half-baked one */
audit_tree_log_remove_rule(context, rule);
- if (entry->rule.exe)
- audit_remove_mark(entry->rule.exe);
rule->tree = NULL;
list_del_rcu(&entry->list);
list_del(&entry->rule.list);
- call_rcu(&entry->rcu, audit_free_rule_rcu);
+ if (rule->exe)
+ need_sync = true;
+ } else {
+ list_del_init(&rule->rlist);
}
}
+
+ if (list_empty(&tree->rules))
+ return;
+
+ if (need_sync)
+ synchronize_rcu();
+
+ list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
+ entry = container_of(rule, struct audit_entry, rule);
+
+ list_del_init(&rule->rlist);
+ if (entry->rule.exe)
+ audit_remove_mark(entry->rule.exe);
+ call_rcu(&entry->rcu, audit_free_rule_rcu);
+ }
}
/*
Regards,
Jérémy
On Tue, Sep 22, 2026 at 10:47 AM Jérémy Jean
<jeremy.jean@oss.cyber.gouv.fr> wrote:
>
> On 2026-09-22 13:26, Ricardo Robaina wrote:
> > On Mon, Sep 21, 2026 at 5:07 PM Jérémy Jean
> > <Jeremy.Jean@oss.cyber.gouv.fr> wrote:
> >>
> >> kill_rules() removes mixed AUDIT_DIR and AUDIT_EXE rules when an audit
> >> tree is pruned. It drops entry->rule.exe before removing the rule from
> >> the RCU-visible filter lists.
> >>
> >> After a rule has been installed with AUDIT_ADD_RULE, which requires
> >> CAP_AUDIT_CONTROL, removing or moving the watched directory can race
> >> with another task that is still evaluating the rule. In that case,
> >> fsnotify can free the executable mark before the reader reaches
> >> audit_mark_compare(), causing a use-after-free.
> >>
> >> KASAN reports:
> >>
> >> BUG: KASAN: slab-use-after-free in audit_mark_compare+0x8d/0xa0
> >>
> >> Remove the rule from the RCU-visible filter lists first, wait for a
> >> grace
> >> period, and only then drop the executable mark. audit_del_rule()
> >> already
> >> uses this ordering.
> >>
> >> Fixes: 34d99af52ad4 ("audit: implement audit by executable")
> >> Assisted-by: Codex:gpt-5
> >> Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
> >> ---
> >> kernel/audit_tree.c | 5 +++--
> >> 1 file changed, 3 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> >> index 1ed19b7..864a58b 100644
> >> --- a/kernel/audit_tree.c
> >> +++ b/kernel/audit_tree.c
> >> @@ -553,11 +553,12 @@ static void kill_rules(struct audit_context
> >> *context, struct audit_tree *tree)
> >> if (rule->tree) {
> >> /* not a half-baked one */
> >> audit_tree_log_remove_rule(context, rule);
> >> - if (entry->rule.exe)
> >> - audit_remove_mark(entry->rule.exe);
> >> rule->tree = NULL;
> >> list_del_rcu(&entry->list);
> >> list_del(&entry->rule.list);
> >> + synchronize_rcu();
> >> + if (entry->rule.exe)
> >> + audit_remove_mark(entry->rule.exe);
> >> call_rcu(&entry->rcu, audit_free_rule_rcu);
> >> }
> >> }
> >> --
> >> 2.47.3
> >>
> >>
> >
> > Hi Jérémy,
> >
> > Thanks for troubleshooting and fixing this bug.
> >
> > sashiko's review makes sense, though: synchronize_rcu() inside the
> > loop waits a full grace period per rule, and kill_rules() runs with
> > audit_filter_mutex held, so a tree with many rules stalls other audit
> > config operations. Below is an untested suggestion to use a single
> > grace period instead.
> >
> > diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> > index 1ed19b775912..5a3d7c7ba5ce 100644
> > --- a/kernel/audit_tree.c
> > +++ b/kernel/audit_tree.c
> > @@ -549,18 +549,30 @@ static void kill_rules(struct audit_context
> > *context, struct audit_tree *tree)
> > list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
> > entry = container_of(rule, struct audit_entry, rule);
> >
> > - list_del_init(&rule->rlist);
> > if (rule->tree) {
> > /* not a half-baked one */
> > audit_tree_log_remove_rule(context, rule);
> > - if (entry->rule.exe)
> > - audit_remove_mark(entry->rule.exe);
> > rule->tree = NULL;
> > list_del_rcu(&entry->list);
> > list_del(&entry->rule.list);
> > - call_rcu(&entry->rcu, audit_free_rule_rcu);
> > + } else {
> > + list_del_init(&rule->rlist);
> > }
> > }
> > +
> > + if (list_empty(&tree->rules))
> > + return;
> > +
> > + synchronize_rcu();
> > +
> > + list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
> > + entry = container_of(rule, struct audit_entry, rule);
> > +
> > + list_del_init(&rule->rlist);
> > + if (entry->rule.exe)
> > + audit_remove_mark(entry->rule.exe);
> > + call_rcu(&entry->rcu, audit_free_rule_rcu);
> > + }
> > }
> >
> > /*
>
> Hello Ricardo,
>
> Many thanks for your nice and constructive answer.
>
> Indeed, sashiko's review makes sense and your suggested v2 is a good
> fix.
> I have replayed my reproducer to ensure that it indeeds fix the reported
> bug.
>
> However, I wonder whether the wait should still happen in the case where
> all removed rules have rule->exe == NULL. Doesn't call_rcu() already
> free (kernel/auditfilter.c:96)? If yes, could we skip synchronize_rcu()
> in
> that case? If this question is valid, how about this fix based on yours,
> which
> simply adds a bool to detect whether synchronize_rcu() should be called.
>
> If you think this addition is good, I can send a v2 with that.
It looks like a nice optimization, good catch! synchronize_rcu() is
usually expensive, so calling it only when necessary is an improvement
for sure.
One minor detail, I'd use 'entry->rule.exe' instead of 'rule->exe' in
the need_sync check just for consistency.
>
> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> index 1ed19b775912..e2cd27b17590 100644
> --- a/kernel/audit_tree.c
> +++ b/kernel/audit_tree.c
> @@ -545,22 +545,38 @@ static void kill_rules(struct audit_context
> *context, struct audit_tree *tree)
> {
> struct audit_krule *rule, *next;
> struct audit_entry *entry;
> + bool need_sync = false;
>
> list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
> entry = container_of(rule, struct audit_entry, rule);
>
> - list_del_init(&rule->rlist);
> if (rule->tree) {
> /* not a half-baked one */
> audit_tree_log_remove_rule(context, rule);
> - if (entry->rule.exe)
> - audit_remove_mark(entry->rule.exe);
> rule->tree = NULL;
> list_del_rcu(&entry->list);
> list_del(&entry->rule.list);
> - call_rcu(&entry->rcu, audit_free_rule_rcu);
> + if (rule->exe)
> + need_sync = true;
> + } else {
> + list_del_init(&rule->rlist);
> }
> }
> +
> + if (list_empty(&tree->rules))
> + return;
> +
> + if (need_sync)
> + synchronize_rcu();
> +
> + list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
> + entry = container_of(rule, struct audit_entry, rule);
> +
> + list_del_init(&rule->rlist);
> + if (entry->rule.exe)
> + audit_remove_mark(entry->rule.exe);
> + call_rcu(&entry->rcu, audit_free_rule_rcu);
> + }
> }
>
> /*
>
> Regards,
> Jérémy
>
--Ricardo
On 22 September 2026 14:46:55 BST, "Jérémy Jean"
<jeremy.jean@oss.cyber.gouv.fr> wrote:
>On 2026-09-22 13:26, Ricardo Robaina wrote:
>> On Mon, Sep 21, 2026 at 5:07 PM Jérémy Jean
>> <Jeremy.Jean@oss.cyber.gouv.fr> wrote:
>>>
>>> kill_rules() removes mixed AUDIT_DIR and AUDIT_EXE rules when an audit
>>> tree is pruned. It drops entry->rule.exe before removing the rule from
>>> the RCU-visible filter lists.
>>>
>>> After a rule has been installed with AUDIT_ADD_RULE, which requires
>>> CAP_AUDIT_CONTROL, removing or moving the watched directory can race
>>> with another task that is still evaluating the rule. In that case,
>>> fsnotify can free the executable mark before the reader reaches
>>> audit_mark_compare(), causing a use-after-free.
>>>
>>> KASAN reports:
>>>
>>> BUG: KASAN: slab-use-after-free in audit_mark_compare+0x8d/0xa0
>>>
>>> Remove the rule from the RCU-visible filter lists first, wait for a
>grace
>>> period, and only then drop the executable mark. audit_del_rule()
>already
>>> uses this ordering.
>>>
>>> Fixes: 34d99af52ad4 ("audit: implement audit by executable")
>>> Assisted-by: Codex:gpt-5
>>> Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
>>> ---
>>> kernel/audit_tree.c | 5 +++--
>>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
>>> index 1ed19b7..864a58b 100644
>>> --- a/kernel/audit_tree.c
>>> +++ b/kernel/audit_tree.c
>>> @@ -553,11 +553,12 @@ static void kill_rules(struct audit_context
>*context, struct audit_tree *tree)
>>> if (rule->tree) {
>>> /* not a half-baked one */
>>> audit_tree_log_remove_rule(context, rule);
>>> - if (entry->rule.exe)
>>> - audit_remove_mark(entry->rule.exe);
>>> rule->tree = NULL;
>>> list_del_rcu(&entry->list);
>>> list_del(&entry->rule.list);
>>> + synchronize_rcu();
>>> + if (entry->rule.exe)
>>> + audit_remove_mark(entry->rule.exe);
>>> call_rcu(&entry->rcu, audit_free_rule_rcu);
>>> }
>>> }
>>> --
>>> 2.47.3
>>>
>>>
>>
>> Hi Jérémy,
>>
>> Thanks for troubleshooting and fixing this bug.
>>
>> sashiko's review makes sense, though: synchronize_rcu() inside the
>> loop waits a full grace period per rule, and kill_rules() runs with
>> audit_filter_mutex held, so a tree with many rules stalls other audit
>> config operations. Below is an untested suggestion to use a single
>> grace period instead.
>>
>> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
>> index 1ed19b775912..5a3d7c7ba5ce 100644
>> --- a/kernel/audit_tree.c
>> +++ b/kernel/audit_tree.c
>> @@ -549,18 +549,30 @@ static void kill_rules(struct audit_context
>> *context, struct audit_tree *tree)
>> list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
>> entry = container_of(rule, struct audit_entry, rule);
>>
>> - list_del_init(&rule->rlist);
>> if (rule->tree) {
>> /* not a half-baked one */
>> audit_tree_log_remove_rule(context, rule);
>> - if (entry->rule.exe)
>> - audit_remove_mark(entry->rule.exe);
>> rule->tree = NULL;
>> list_del_rcu(&entry->list);
>> list_del(&entry->rule.list);
>> - call_rcu(&entry->rcu, audit_free_rule_rcu);
>> + } else {
>> + list_del_init(&rule->rlist);
>> }
>> }
>> +
>> + if (list_empty(&tree->rules))
>> + return;
>> +
>> + synchronize_rcu();
>> +
>> + list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
>> + entry = container_of(rule, struct audit_entry, rule);
>> +
>> + list_del_init(&rule->rlist);
>> + if (entry->rule.exe)
>> + audit_remove_mark(entry->rule.exe);
>> + call_rcu(&entry->rcu, audit_free_rule_rcu);
>> + }
>> }
>>
>> /*
>
>Hello Ricardo,
>
>Many thanks for your nice and constructive answer.
>
>Indeed, sashiko's review makes sense and your suggested v2 is a good fix.
>I have replayed my reproducer to ensure that it indeeds fix the reported
>bug.
>
>However, I wonder whether the wait should still happen in the case where
>all removed rules have rule->exe == NULL. Doesn't call_rcu() already
>free (kernel/auditfilter.c:96)? If yes, could we skip synchronize_rcu()
>in
>that case? If this question is valid, how about this fix based on yours,
>which
>simply adds a bool to detect whether synchronize_rcu() should be called.
>
>If you think this addition is good, I can send a v2 with that.
>
>diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
>index 1ed19b775912..e2cd27b17590 100644
>--- a/kernel/audit_tree.c
>+++ b/kernel/audit_tree.c
>@@ -545,22 +545,38 @@ static void kill_rules(struct audit_context *context, struct audit_tree *tree)
> {
> struct audit_krule *rule, *next;
> struct audit_entry *entry;
>+ bool need_sync = false;
>
> list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
> entry = container_of(rule, struct audit_entry, rule);
>
>- list_del_init(&rule->rlist);
> if (rule->tree) {
> /* not a half-baked one */
> audit_tree_log_remove_rule(context, rule);
>- if (entry->rule.exe)
>- audit_remove_mark(entry->rule.exe);
> rule->tree = NULL;
> list_del_rcu(&entry->list);
> list_del(&entry->rule.list);
>- call_rcu(&entry->rcu, audit_free_rule_rcu);
>+ if (rule->exe)
>+ need_sync = true;
>+ } else {
>+ list_del_init(&rule->rlist);
> }
> }
>+
>+ if (list_empty(&tree->rules))
>+ return;
>+
>+ if (need_sync)
>+ synchronize_rcu();
>+
>+ list_for_each_entry_safe(rule, next, &tree->rules, rlist) {
>+ entry = container_of(rule, struct audit_entry, rule);
>+
>+ list_del_init(&rule->rlist);
>+ if (entry->rule.exe)
>+ audit_remove_mark(entry->rule.exe);
>+ call_rcu(&entry->rcu, audit_free_rule_rcu);
>+ }
> }
>
> /*
LGTM!
Reviewed-by: Bradley Morgan <brads@mainlining.org>
What do you reckon Ricardo?
>
>Regards,
>Jérémy
--- Thanks!
"I'm not a very positive person" - Linus torvalds
On 21 September 2026 20:59:22 BST, "Jérémy Jean"
<Jeremy.Jean@oss.cyber.gouv.fr> wrote:
>kill_rules() removes mixed AUDIT_DIR and AUDIT_EXE rules when an audit
>tree is pruned. It drops entry->rule.exe before removing the rule from
>the RCU-visible filter lists.
>
>After a rule has been installed with AUDIT_ADD_RULE, which requires
>CAP_AUDIT_CONTROL, removing or moving the watched directory can race
>with another task that is still evaluating the rule. In that case,
>fsnotify can free the executable mark before the reader reaches
>audit_mark_compare(), causing a use-after-free.
>
>KASAN reports:
>
> BUG: KASAN: slab-use-after-free in audit_mark_compare+0x8d/0xa0
>
>Remove the rule from the RCU-visible filter lists first, wait for a grace
>period, and only then drop the executable mark. audit_del_rule() already
>uses this ordering.
>
>Fixes: 34d99af52ad4 ("audit: implement audit by executable")
>Assisted-by: Codex:gpt-5
NAK, read sashiko and generate a V2, and then CC me.
>Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
>---
> kernel/audit_tree.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
>diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
>index 1ed19b7..864a58b 100644
>--- a/kernel/audit_tree.c
>+++ b/kernel/audit_tree.c
>@@ -553,11 +553,12 @@ static void kill_rules(struct audit_context *context, struct audit_tree *tree)
> if (rule->tree) {
> /* not a half-baked one */
> audit_tree_log_remove_rule(context, rule);
>- if (entry->rule.exe)
>- audit_remove_mark(entry->rule.exe);
> rule->tree = NULL;
> list_del_rcu(&entry->list);
> list_del(&entry->rule.list);
>+ synchronize_rcu();
>+ if (entry->rule.exe)
>+ audit_remove_mark(entry->rule.exe);
> call_rcu(&entry->rcu, audit_free_rule_rcu);
> }
> }
>
--- Thanks!
"I'm not a very positive person" - Linus torvalds
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