* [PATCH v5 1/9] of: hold a reference on of_aliases during alias path resolution
2026-07-23 3:19 [PATCH v5 0/9] of: teach overlay code to keep /aliases in sync Abdurrahman Hussain
@ 2026-07-23 3:19 ` Abdurrahman Hussain
2026-07-23 3:35 ` sashiko-bot
2026-07-23 3:19 ` [PATCH v5 2/9] of: update /aliases lookup on reconfig notifications Abdurrahman Hussain
` (7 subsequent siblings)
8 siblings, 1 reply; 16+ messages in thread
From: Abdurrahman Hussain @ 2026-07-23 3:19 UTC (permalink / raw)
To: Rob Herring, Saravana Kannan, Frank Rowand
Cc: devicetree, linux-kernel, Abdurrahman Hussain
of_find_node_opts_by_path() walks the property list of of_aliases
without taking a reference on the node and passes pp->value straight
to of_find_node_by_path().
Take a reference across the walk. The walk itself stays lock-free
like every other property iteration: removed properties keep their
->next and are only freed when the node is released, so the node
reference is sufficient. devtree_lock covers only the pointer load,
pairing it with a later patch in this series that clears of_aliases
and drops its reference when the node is detached at runtime.
Validate the value before resolving it. of_alias_value_ok() requires
a non-empty, NUL-terminated, absolute path:
- an empty property has a NULL value and crashes in strchr()
- a value without a NUL inside the property is read past its end
- a relative value naming another alias (loop = "loop") recurses
through of_find_node_by_path() until the stack is exhausted
All three are reachable with a malformed boot FDT today.
The name comparison loses its redundant strlen() pass while here.
Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
drivers/of/base.c | 20 +++++++++++++++-----
drivers/of/of_private.h | 8 ++++++++
2 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/drivers/of/base.c b/drivers/of/base.c
index 6e7a42dedad3..6f79f593fc77 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -995,6 +995,8 @@ struct device_node *of_find_node_opts_by_path(const char *path, const char **opt
/* The path could begin with an alias */
if (*path != '/') {
+ struct device_node *aliases;
+ const char *value = NULL;
int len;
const char *p = strchrnul(path, '/');
@@ -1002,16 +1004,24 @@ struct device_node *of_find_node_opts_by_path(const char *path, const char **opt
p = separator;
len = p - path;
- /* of_aliases must not be NULL */
- if (!of_aliases)
+ /* the load pairs with writers that retire the node */
+ raw_spin_lock_irqsave(&devtree_lock, flags);
+ aliases = of_node_get(of_aliases);
+ raw_spin_unlock_irqrestore(&devtree_lock, flags);
+ if (!aliases)
return NULL;
- for_each_property_of_node(of_aliases, pp) {
- if (strlen(pp->name) == len && !strncmp(pp->name, path, len)) {
- np = of_find_node_by_path(pp->value);
+ for_each_property_of_node(aliases, pp) {
+ if (!strncmp(pp->name, path, len) && !pp->name[len]) {
+ if (of_alias_value_ok(pp))
+ value = pp->value;
break;
}
}
+ /* the reference on @aliases keeps @value alive */
+ if (value)
+ np = of_find_node_by_path(value);
+ of_node_put(aliases);
if (!np)
return NULL;
path = p;
diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
index 0ae16da066e2..9bba999f0bf8 100644
--- a/drivers/of/of_private.h
+++ b/drivers/of/of_private.h
@@ -215,6 +215,14 @@ static inline bool is_pseudo_property(const char *prop_name)
!of_prop_cmp(prop_name, "linux,phandle");
}
+/* alias values must be absolute paths NUL-terminated within length */
+static inline bool of_alias_value_ok(const struct property *pp)
+{
+ return pp->value && pp->length >= 2 &&
+ *(const char *)pp->value == '/' &&
+ strnlen(pp->value, pp->length) < pp->length;
+}
+
#if IS_ENABLED(CONFIG_KUNIT)
int __of_address_resource_bounds(struct resource *r, u64 start, u64 size);
#endif
--
2.54.0
^ permalink raw reply related [flat|nested] 16+ messages in thread* Re: [PATCH v5 1/9] of: hold a reference on of_aliases during alias path resolution
2026-07-23 3:19 ` [PATCH v5 1/9] of: hold a reference on of_aliases during alias path resolution Abdurrahman Hussain
@ 2026-07-23 3:35 ` sashiko-bot
2026-07-23 17:07 ` Abdurrahman Hussain
0 siblings, 1 reply; 16+ messages in thread
From: sashiko-bot @ 2026-07-23 3:35 UTC (permalink / raw)
To: Abdurrahman Hussain; +Cc: robh, conor+dt, devicetree
Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
Pre-existing issues:
- [High] Calling of_node_put() while holding a raw spinlock causes a sleep-in-atomic bug if it drops the last reference to a dynamic node.
- [High] Lockless iteration of device tree properties is unsafe because updated or removed properties have their `next` pointer modified, which derails concurrent readers.
--
--- Patch [1]: [PATCH v5 1/9] of: hold a reference on of_aliases during alias path resolution ---
commit aa90279de0a9f76f84e2b40b29743f11984c3ffb
Author: Abdurrahman Hussain <abdurrahman@nexthop.ai>
Subject: of: hold a reference on of_aliases during alias path resolution
This patch modifies of_find_node_opts_by_path to hold a reference to
of_aliases during alias path resolution. It also validates the alias value
to prevent crashes or infinite recursion with malformed device trees.
> Take a reference across the walk. The walk itself stays lock-free
> like every other property iteration: removed properties keep their
> ->next and are only freed when the node is released, so the node
> reference is sufficient.
[Severity: High]
This isn't a bug introduced by this patch, but is the description of the
lock-free walk accurate?
Looking at __of_remove_property() and __of_update_property(), when a
property is removed, it is moved to the node's deadprops list:
drivers/of/base.c:__of_remove_property() {
...
/* Found the property, add it to deadprops list */
prop->next = np->deadprops;
np->deadprops = prop;
...
}
If a concurrent writer (e.g., overlay application) removes a property while
for_each_property_of_node() is iterating over it, won't the reader's next
access of pp->next follow the pointer into the deadprops list?
This would cause the reader to traverse the dead properties and skip the
remaining valid properties in np->properties, potentially causing spurious
lookup failures.
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 6e7a42dedad3f..6f79f593fc779 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
[ ... ]
> @@ -1002,16 +1004,24 @@ struct device_node *of_find_node_opts_by_path(const char *path, const char **opt
> p = separator;
> len = p - path;
>
> - /* of_aliases must not be NULL */
> - if (!of_aliases)
> + /* the load pairs with writers that retire the node */
> + raw_spin_lock_irqsave(&devtree_lock, flags);
> + aliases = of_node_get(of_aliases);
> + raw_spin_unlock_irqrestore(&devtree_lock, flags);
> + if (!aliases)
> return NULL;
>
> - for_each_property_of_node(of_aliases, pp) {
> - if (strlen(pp->name) == len && !strncmp(pp->name, path, len)) {
> - np = of_find_node_by_path(pp->value);
> + for_each_property_of_node(aliases, pp) {
> + if (!strncmp(pp->name, path, len) && !pp->name[len]) {
> + if (of_alias_value_ok(pp))
> + value = pp->value;
> break;
> }
> }
> + /* the reference on @aliases keeps @value alive */
> + if (value)
> + np = of_find_node_by_path(value);
> + of_node_put(aliases);
> if (!np)
> return NULL;
> path = p;
[Severity: High]
This is a pre-existing issue, but does calling __of_find_node_by_full_path()
while holding devtree_lock further down in this function risk a
sleep-in-atomic bug?
Right after this block in of_find_node_opts_by_path(), devtree_lock (which is
a raw spinlock) is acquired around __of_find_node_by_full_path():
drivers/of/base.c:of_find_node_opts_by_path() {
...
/* Step down the tree matching path components */
raw_spin_lock_irqsave(&devtree_lock, flags);
if (!np)
np = of_node_get(of_root);
np = __of_find_node_by_full_path(np, path);
raw_spin_unlock_irqrestore(&devtree_lock, flags);
...
}
Inside __of_find_node_by_full_path(), it iteratively drops node references:
drivers/of/base.c:__of_find_node_by_full_path() {
...
node = __of_find_node_by_path(node, path);
of_node_put(tmp);
...
}
If a parallel thread (such as an overlay removal) detaches a dynamic node,
its primary tree reference is dropped.
If of_node_put() drops the last reference to that node while held under the
raw spinlock, won't it synchronously invoke of_node_release()?
For dynamic nodes, of_node_release() calls fwnode_links_purge(), which
acquires fwnode_link_lock (a sleeping mutex), resulting in a sleep-in-atomic
scenario.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260722-nh-of-alias-overlay-v5-0-2abe2bb9cdbc@nexthop.ai?part=1
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [PATCH v5 1/9] of: hold a reference on of_aliases during alias path resolution
2026-07-23 3:35 ` sashiko-bot
@ 2026-07-23 17:07 ` Abdurrahman Hussain
0 siblings, 0 replies; 16+ messages in thread
From: Abdurrahman Hussain @ 2026-07-23 17:07 UTC (permalink / raw)
To: sashiko-reviews
Cc: robh, saravanak, frowand.list, krzk, devicetree, linux-kernel
On Tue Jul 22, 2026 at 8:35 PM PDT, sashiko-bot wrote:
> [Severity: High]
> This isn't a bug introduced by this patch, but is the description of the
> lock-free walk accurate?
>
> If a concurrent writer (e.g., overlay application) removes a property while
> for_each_property_of_node() is iterating over it, won't the reader's next
> access of pp->next follow the pointer into the deadprops list?
Right, the commit message misstates the mechanism.
__of_remove_property() repoints prop->next at the deadprops head, so
a racing walker can be diverted into deadprops and miss live
properties. What it cannot do is step into freed memory while it
holds the node reference: dead properties are only freed at node
release. So the conclusion stands (the walk is memory-safe without
the lock) but the failure mode is a stale view, the same as every
other lock-free property walk in the tree. I'll fix the wording in
the next revision.
> [Severity: High]
> This is a pre-existing issue, but does calling __of_find_node_by_full_path()
> while holding devtree_lock further down in this function risk a
> sleep-in-atomic bug?
Known, and tracked in the cover letter's open items. It affects every
OF iterator that puts nodes under devtree_lock and needs a series of
its own.
Thanks,
Abdurrahman
^ permalink raw reply [flat|nested] 16+ messages in thread
* [PATCH v5 2/9] of: update /aliases lookup on reconfig notifications
2026-07-23 3:19 [PATCH v5 0/9] of: teach overlay code to keep /aliases in sync Abdurrahman Hussain
2026-07-23 3:19 ` [PATCH v5 1/9] of: hold a reference on of_aliases during alias path resolution Abdurrahman Hussain
@ 2026-07-23 3:19 ` Abdurrahman Hussain
2026-07-23 3:34 ` sashiko-bot
2026-07-23 3:19 ` [PATCH v5 3/9] of/overlay: look up absolute target-paths absolutely Abdurrahman Hussain
` (6 subsequent siblings)
8 siblings, 1 reply; 16+ messages in thread
From: Abdurrahman Hussain @ 2026-07-23 3:19 UTC (permalink / raw)
To: Rob Herring, Saravana Kannan, Frank Rowand
Cc: devicetree, linux-kernel, Abdurrahman Hussain
Aliases added by overlays never make it into aliases_lookup, which is
only filled by of_alias_scan() at boot. of_alias_get_id() returns
-ENODEV for them and drivers using alias based numbering (i2c, spi,
tty, mmc) fall back to dynamic ids.
Register a reconfig notifier and mirror /aliases property changes
into aliases_lookup. The notifier chain covers changesets and
overlays, so no overlay specific hook is needed. Same approach as
Geert's 2015 series [1], which was never reposted;
of_alias_create()/of_alias_destroy() keep its names.
The /aliases node is matched by name and root parent instead of the
of_aliases pointer, which is still NULL when an overlay creates the
node on a system without a boot-time /aliases. The name match is
exact, of_node_name_eq() would also match "aliases@1". ATTACH stores
the node in of_aliases with a reference held, DETACH drops it again
and flushes aliases_lookup; the pointer updates happen under
devtree_lock to pair with the reader in of_find_node_opts_by_path().
Nodes attached with properties already set are not scanned, as
before.
Lookup entries are created by of_alias_scan()'s old loop body, moved
into of_alias_create(). Entries created at runtime have kstrdup'ed
names and an of_node_get'ed target and are flagged "owned" so
of_alias_destroy() knows what to kfree(); boot entries live in
memblock and are only unlinked. Removal matches entries regardless of
ownership so updating a boot-time alias does not leave duplicates
behind, which was Grant's main concern on the old series [2].
A new aliases_mutex protects the list. of_mutex does not work here:
the notifier runs under it on the overlay path but outside of it on
the of_add_property() path.
The rework also fixes an out-of-bounds read in the old stem parser,
which tested isdigit(*(end - 1)) before checking end > start and so
read one byte before the property name when the name was empty or all
digits. Such names are skipped now instead of getting an empty stem.
Only built for CONFIG_OF_DYNAMIC: there are no notifications without
it and the register stub returns -EINVAL.
Link: https://lore.kernel.org/lkml/1435675876-2159-1-git-send-email-geert+renesas@glider.be/ [1]
Link: https://lore.kernel.org/lkml/20150630172131.D4E6CC4041A@trevor.secretlab.ca/ [2]
Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
drivers/of/base.c | 210 +++++++++++++++++++++++++++++++++++++++---------
drivers/of/device.c | 4 +-
drivers/of/of_private.h | 14 ++++
3 files changed, 186 insertions(+), 42 deletions(-)
diff --git a/drivers/of/base.c b/drivers/of/base.c
index 6f79f593fc77..612e2cd31688 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1925,6 +1925,170 @@ static void of_alias_add(struct alias_prop *ap, struct device_node *np,
ap->alias, ap->stem, ap->id, np);
}
+/*
+ * Protects aliases_lookup and of_aliases. of_alias_scan() runs single-
+ * threaded at init and skips it; every other reader/writer must hold it.
+ */
+DEFINE_MUTEX(aliases_mutex);
+
+/* Callers other than of_alias_scan() must hold @aliases_mutex. */
+static void of_alias_create(const struct property *pp,
+ void *(*dt_alloc)(u64 size, u64 align),
+ bool owned)
+{
+ const char *start = pp->name;
+ const char *end;
+ struct device_node *np;
+ struct alias_prop *ap;
+ const char *dup;
+ int id, len;
+
+ if (is_pseudo_property(pp->name))
+ return;
+
+ if (!of_alias_value_ok(pp))
+ return;
+
+ np = of_find_node_by_path(pp->value);
+ if (!np)
+ return;
+
+ end = start + strlen(start);
+ while (end > start && isdigit(*(end - 1)))
+ end--;
+ len = end - start;
+ if (len == 0)
+ goto out_put;
+
+ if (kstrtoint(end, 10, &id) < 0)
+ goto out_put;
+
+ ap = dt_alloc(sizeof(*ap) + len + 1, __alignof__(*ap));
+ if (!ap)
+ goto out_put;
+ memset(ap, 0, sizeof(*ap) + len + 1);
+
+ if (owned) {
+ dup = kstrdup(pp->name, GFP_KERNEL);
+ if (!dup) {
+ kfree(ap);
+ goto out_put;
+ }
+ } else {
+ dup = start;
+ }
+ ap->alias = dup;
+ ap->owned = owned;
+ of_alias_add(ap, np, id, start, len);
+ return;
+
+out_put:
+ of_node_put(np);
+}
+
+#ifdef CONFIG_OF_DYNAMIC
+/* Unlink @ap; free its storage if it was runtime-allocated. */
+static void __of_alias_del(struct alias_prop *ap)
+{
+ list_del(&ap->link);
+ of_node_put(ap->np);
+ if (ap->owned) {
+ kfree(ap->alias);
+ kfree(ap);
+ }
+}
+
+/* Callers must hold @aliases_mutex. */
+static void of_alias_destroy(const char *name)
+{
+ struct alias_prop *ap, *tmp;
+
+ list_for_each_entry_safe(ap, tmp, &aliases_lookup, link) {
+ if (strcmp(ap->alias, name) != 0)
+ continue;
+ __of_alias_del(ap);
+ return;
+ }
+}
+
+static void *alias_alloc(u64 size, u64 align)
+{
+ return kzalloc(size, GFP_KERNEL);
+}
+
+/* Callers must hold @aliases_mutex. */
+static void of_aliases_forget_all(void)
+{
+ struct alias_prop *ap, *tmp;
+
+ list_for_each_entry_safe(ap, tmp, &aliases_lookup, link)
+ __of_alias_del(ap);
+}
+
+static int of_aliases_reconfig_notifier(struct notifier_block *nb,
+ unsigned long action, void *arg)
+{
+ struct of_reconfig_data *rd = arg;
+ struct device_node *put = NULL;
+ unsigned long flags;
+
+ /* of_aliases may still be NULL when an overlay creates the node */
+ if (!rd->dn || !of_node_is_aliases(rd->dn))
+ return NOTIFY_DONE;
+
+ mutex_lock(&aliases_mutex);
+ switch (action) {
+ case OF_RECONFIG_ATTACH_NODE:
+ /* of_aliases is read under devtree_lock by alias path lookup */
+ raw_spin_lock_irqsave(&devtree_lock, flags);
+ if (!of_aliases)
+ of_aliases = of_node_get(rd->dn);
+ raw_spin_unlock_irqrestore(&devtree_lock, flags);
+ break;
+ case OF_RECONFIG_DETACH_NODE:
+ raw_spin_lock_irqsave(&devtree_lock, flags);
+ if (of_aliases == rd->dn) {
+ of_aliases = NULL;
+ put = rd->dn;
+ }
+ raw_spin_unlock_irqrestore(&devtree_lock, flags);
+ if (put) {
+ of_aliases_forget_all();
+ /* may free the node, so must sit outside devtree_lock */
+ of_node_put(put);
+ }
+ break;
+ case OF_RECONFIG_ADD_PROPERTY:
+ of_alias_create(rd->prop, alias_alloc, true);
+ break;
+ case OF_RECONFIG_REMOVE_PROPERTY:
+ of_alias_destroy(rd->prop->name);
+ break;
+ case OF_RECONFIG_UPDATE_PROPERTY:
+ if (rd->old_prop)
+ of_alias_destroy(rd->old_prop->name);
+ of_alias_create(rd->prop, alias_alloc, true);
+ break;
+ default:
+ break;
+ }
+ mutex_unlock(&aliases_mutex);
+ return NOTIFY_OK;
+}
+
+static struct notifier_block of_aliases_nb = {
+ .notifier_call = of_aliases_reconfig_notifier,
+};
+
+static int __init of_aliases_reconfig_init(void)
+{
+ return of_reconfig_notifier_register(&of_aliases_nb);
+}
+
+/* of_alias_scan() runs pre-initcall, so the boot-time scan is complete */
+core_initcall_sync(of_aliases_reconfig_init);
+#endif /* CONFIG_OF_DYNAMIC */
+
/**
* of_alias_scan - Scan all properties of the 'aliases' node
* @dt_alloc: An allocator that provides a virtual address to memory
@@ -1960,42 +2124,8 @@ void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align))
if (!of_aliases)
return;
- for_each_property_of_node(of_aliases, pp) {
- const char *start = pp->name;
- const char *end = start + strlen(start);
- struct device_node *np;
- struct alias_prop *ap;
- int id, len;
-
- /* Skip those we do not want to proceed */
- if (is_pseudo_property(pp->name))
- continue;
-
- np = of_find_node_by_path(pp->value);
- if (!np)
- continue;
-
- /* walk the alias backwards to extract the id and work out
- * the 'stem' string */
- while (isdigit(*(end-1)) && end > start)
- end--;
- len = end - start;
-
- if (kstrtoint(end, 10, &id) < 0) {
- of_node_put(np);
- continue;
- }
-
- /* Allocate an alias_prop with enough space for the stem */
- ap = dt_alloc(sizeof(*ap) + len + 1, __alignof__(*ap));
- if (!ap) {
- of_node_put(np);
- continue;
- }
- memset(ap, 0, sizeof(*ap) + len + 1);
- ap->alias = start;
- of_alias_add(ap, np, id, start, len);
- }
+ for_each_property_of_node(of_aliases, pp)
+ of_alias_create(pp, dt_alloc, false);
}
/**
@@ -2013,7 +2143,7 @@ int of_alias_get_id(const struct device_node *np, const char *stem)
struct alias_prop *app;
int id = -ENODEV;
- mutex_lock(&of_mutex);
+ mutex_lock(&aliases_mutex);
list_for_each_entry(app, &aliases_lookup, link) {
if (strcmp(app->stem, stem) != 0)
continue;
@@ -2023,7 +2153,7 @@ int of_alias_get_id(const struct device_node *np, const char *stem)
break;
}
}
- mutex_unlock(&of_mutex);
+ mutex_unlock(&aliases_mutex);
return id;
}
@@ -2041,7 +2171,7 @@ int of_alias_get_highest_id(const char *stem)
struct alias_prop *app;
int id = -ENODEV;
- mutex_lock(&of_mutex);
+ mutex_lock(&aliases_mutex);
list_for_each_entry(app, &aliases_lookup, link) {
if (strcmp(app->stem, stem) != 0)
continue;
@@ -2049,7 +2179,7 @@ int of_alias_get_highest_id(const char *stem)
if (app->id > id)
id = app->id;
}
- mutex_unlock(&of_mutex);
+ mutex_unlock(&aliases_mutex);
return id;
}
diff --git a/drivers/of/device.c b/drivers/of/device.c
index b3dc78f2fa3a..fa0cc8129ab0 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -237,7 +237,7 @@ void of_device_uevent(const struct device *dev, struct kobj_uevent_env *env)
add_uevent_var(env, "OF_COMPATIBLE_N=%d", seen);
seen = 0;
- mutex_lock(&of_mutex);
+ mutex_lock(&aliases_mutex);
list_for_each_entry(app, &aliases_lookup, link) {
if (dev->of_node == app->np) {
add_uevent_var(env, "OF_ALIAS_%d=%s", seen,
@@ -245,7 +245,7 @@ void of_device_uevent(const struct device *dev, struct kobj_uevent_env *env)
seen++;
}
}
- mutex_unlock(&of_mutex);
+ mutex_unlock(&aliases_mutex);
}
EXPORT_SYMBOL_GPL(of_device_uevent);
diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
index 9bba999f0bf8..731b606ae3e3 100644
--- a/drivers/of/of_private.h
+++ b/drivers/of/of_private.h
@@ -17,6 +17,11 @@
* @alias: Alias property name
* @np: Pointer to device_node that the alias stands for
* @id: Index value from end of alias name
+ * @owned: True for runtime entries, where the struct and @alias are
+ * kmalloc'd/kstrdup'd and freed on removal. False for boot-time
+ * entries, which live in memblock (@alias points into the FDT)
+ * and are only unlinked. Every entry holds a reference on @np;
+ * removal drops it regardless of @owned.
* @stem: Alias string without the index
*
* The structure represents one alias property of 'aliases' node as
@@ -27,6 +32,7 @@ struct alias_prop {
const char *alias;
struct device_node *np;
int id;
+ bool owned;
char stem[];
};
@@ -40,6 +46,7 @@ struct alias_prop {
extern struct mutex of_mutex;
extern raw_spinlock_t devtree_lock;
+extern struct mutex aliases_mutex;
extern struct list_head aliases_lookup;
extern struct kset *of_kset;
@@ -223,6 +230,13 @@ static inline bool of_alias_value_ok(const struct property *pp)
strnlen(pp->value, pp->length) < pp->length;
}
+/* the /aliases node: root child with the exact name "aliases" */
+static inline bool of_node_is_aliases(const struct device_node *np)
+{
+ return of_node_is_root(np->parent) &&
+ !strcmp(kbasename(np->full_name), "aliases");
+}
+
#if IS_ENABLED(CONFIG_KUNIT)
int __of_address_resource_bounds(struct resource *r, u64 start, u64 size);
#endif
--
2.54.0
^ permalink raw reply related [flat|nested] 16+ messages in thread* Re: [PATCH v5 2/9] of: update /aliases lookup on reconfig notifications
2026-07-23 3:19 ` [PATCH v5 2/9] of: update /aliases lookup on reconfig notifications Abdurrahman Hussain
@ 2026-07-23 3:34 ` sashiko-bot
0 siblings, 0 replies; 16+ messages in thread
From: sashiko-bot @ 2026-07-23 3:34 UTC (permalink / raw)
To: Abdurrahman Hussain; +Cc: robh, conor+dt, devicetree
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues:
- [High] Lockless iteration over `aliases->properties` in `of_find_node_opts_by_path()` races with concurrent property additions/removals.
--
--- Patch [2]: [PATCH v5 2/9] of: update /aliases lookup on reconfig notifications ---
commit 9797d916f1b83a48a93f588ed426470feb4bed4a
Author: Abdurrahman Hussain <abdurrahman@nexthop.ai>
of: update /aliases lookup on reconfig notifications
Registers a reconfig notifier to mirror /aliases property changes into
aliases_lookup. The notifier chain covers changesets and overlays, matching
the /aliases node by name and root parent.
Link: https://lore.kernel.org/lkml/1435675876-2159-1-git-send-email-geert+renesas@glider.be/
Link: https://lore.kernel.org/lkml/20150630172131.D4E6CC4041A@trevor.secretlab.ca/
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 6f79f593fc779..612e2cd31688d 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
[ ... ]
> + case OF_RECONFIG_ADD_PROPERTY:
> + of_alias_create(rd->prop, alias_alloc, true);
> + break;
> + case OF_RECONFIG_REMOVE_PROPERTY:
> + of_alias_destroy(rd->prop->name);
> + break;
> + case OF_RECONFIG_UPDATE_PROPERTY:
> + if (rd->old_prop)
> + of_alias_destroy(rd->old_prop->name);
> + of_alias_create(rd->prop, alias_alloc, true);
> + break;
[Severity: High]
This isn't a bug introduced by this patch, but can this concurrent property
addition or removal race with the lockless property iteration in
of_find_node_opts_by_path()?
In drivers/of/base.c:of_find_node_opts_by_path(), aliases->properties is
iterated locklessly:
for_each_property_of_node(aliases, pp) {
if (!strncmp(pp->name, path, len) && !pp->name[len]) {
if (of_alias_value_ok(pp))
value = pp->value;
break;
}
}
Concurrent property modifications via __of_add_property() or
__of_update_property() manipulate the list pointers without memory barriers.
A lockless reader may traverse to a newly added property before its contents
(like pp->name) are globally visible, leading to a crash. Additionally,
__of_update_property() repoints oldprop->next to deadprops, which can divert
a lockless reader into the dead properties list.
Could taking devtree_lock during the iteration, or utilizing the newly
synchronized aliases_lookup list, prevent this race?
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260722-nh-of-alias-overlay-v5-0-2abe2bb9cdbc@nexthop.ai?part=2
^ permalink raw reply [flat|nested] 16+ messages in thread
* [PATCH v5 3/9] of/overlay: look up absolute target-paths absolutely
2026-07-23 3:19 [PATCH v5 0/9] of: teach overlay code to keep /aliases in sync Abdurrahman Hussain
2026-07-23 3:19 ` [PATCH v5 1/9] of: hold a reference on of_aliases during alias path resolution Abdurrahman Hussain
2026-07-23 3:19 ` [PATCH v5 2/9] of: update /aliases lookup on reconfig notifications Abdurrahman Hussain
@ 2026-07-23 3:19 ` Abdurrahman Hussain
2026-07-23 3:19 ` [PATCH v5 4/9] of/overlay: put property on deadprops only after changeset add succeeds Abdurrahman Hussain
` (5 subsequent siblings)
8 siblings, 0 replies; 16+ messages in thread
From: Abdurrahman Hussain @ 2026-07-23 3:19 UTC (permalink / raw)
To: Rob Herring, Saravana Kannan, Frank Rowand
Cc: devicetree, linux-kernel, Abdurrahman Hussain
find_target() with a non-NULL target base concatenates the base path
and the fragment's target-path via "%pOF%s": target-path="/foo"
resolves to "<base>/foo" and can never reach the DT root. An overlay
applied with a base cannot both extend the base subtree and add
/aliases entries, which is what a PCI device declaring its
peripherals under dev_of_node() needs for alias-based bus numbering.
Treat any non-empty target-path as absolute. An empty target-path
still means the base itself, the only form used by the one in-tree
caller passing a base (drivers/misc/lan966x_pci.c).
Spell the contract out in the kernel-doc for @base/@target_base and
in find_target()'s strategy comment.
Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
drivers/of/overlay.c | 38 ++++++++++++++++++--------------------
1 file changed, 18 insertions(+), 20 deletions(-)
diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index 08d5351746be..74aea704835a 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -688,12 +688,15 @@ static int build_changeset(struct overlay_changeset *ovcs)
*
* 1) "target" property containing the phandle of the target
* 2) "target-path" property containing the path of the target
+ *
+ * With a non-NULL @target_base, an empty "target-path" means
+ * @target_base itself; any non-empty "target-path" is resolved
+ * absolutely from the live-tree root.
*/
static struct device_node *find_target(const struct device_node *info_node,
const struct device_node *target_base)
{
struct device_node *node;
- char *target_path;
const char *path;
u32 val;
int ret;
@@ -709,23 +712,14 @@ static struct device_node *find_target(const struct device_node *info_node,
ret = of_property_read_string(info_node, "target-path", &path);
if (!ret) {
- if (target_base) {
- target_path = kasprintf(GFP_KERNEL, "%pOF%s", target_base, path);
- if (!target_path)
- return NULL;
- node = of_find_node_by_path(target_path);
- if (!node) {
- pr_err("find target, node: %pOF, path '%s' not found\n",
- info_node, target_path);
- }
- kfree(target_path);
- } else {
- node = of_find_node_by_path(path);
- if (!node) {
- pr_err("find target, node: %pOF, path '%s' not found\n",
- info_node, path);
- }
- }
+ /* an empty target-path means the target base itself */
+ if (target_base && path[0] == '\0')
+ return of_node_get((struct device_node *)target_base);
+
+ node = of_find_node_by_path(path);
+ if (!node)
+ pr_err("find target, node: %pOF, path '%s' not found\n",
+ info_node, path);
return node;
}
@@ -737,7 +731,9 @@ static struct device_node *find_target(const struct device_node *info_node,
/**
* init_overlay_changeset() - initialize overlay changeset from overlay tree
* @ovcs: Overlay changeset to build
- * @target_base: Point to the target node to apply overlay
+ * @target_base: Target for fragments with an empty "target-path";
+ * fragments with a non-empty "target-path" resolve
+ * absolutely and ignore @target_base
*
* Initialize @ovcs. Populate @ovcs->fragments with node information from
* the top level of @overlay_root. The relevant top level nodes are the
@@ -982,7 +978,9 @@ static int of_overlay_apply(struct overlay_changeset *ovcs,
* @overlay_fdt: pointer to overlay FDT
* @overlay_fdt_size: number of bytes in @overlay_fdt
* @ret_ovcs_id: pointer for returning created changeset id
- * @base: pointer for the target node to apply overlay
+ * @base: target for fragments with an empty "target-path";
+ * fragments with a non-empty "target-path" resolve
+ * absolutely and ignore @base
*
* Creates and applies an overlay changeset.
*
--
2.54.0
^ permalink raw reply related [flat|nested] 16+ messages in thread* [PATCH v5 4/9] of/overlay: put property on deadprops only after changeset add succeeds
2026-07-23 3:19 [PATCH v5 0/9] of: teach overlay code to keep /aliases in sync Abdurrahman Hussain
` (2 preceding siblings ...)
2026-07-23 3:19 ` [PATCH v5 3/9] of/overlay: look up absolute target-paths absolutely Abdurrahman Hussain
@ 2026-07-23 3:19 ` Abdurrahman Hussain
2026-07-23 3:19 ` [PATCH v5 5/9] of/overlay: don't keep a negative id in ovcs->id on idr_alloc() failure Abdurrahman Hussain
` (4 subsequent siblings)
8 siblings, 0 replies; 16+ messages in thread
From: Abdurrahman Hussain @ 2026-07-23 3:19 UTC (permalink / raw)
To: Rob Herring, Saravana Kannan, Frank Rowand
Cc: devicetree, linux-kernel, Abdurrahman Hussain
add_changeset_property() links a new property of a not-yet-live
target node into the node's deadprops list before handing it to
of_changeset_add_property(). If that fails, the error path frees the
property but leaves the freed pointer linked in deadprops, and
of_node_release() frees it a second time when the aborted overlay's
node is released.
Record the changeset entry first and link the property into deadprops
only on success. of_changeset_add_property() never looks at the
node's property lists, so the order of the two steps is otherwise
immaterial, and the error path frees a property that nothing
references.
Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
drivers/of/overlay.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index 74aea704835a..284c9bc6c9cf 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -358,12 +358,13 @@ static int add_changeset_property(struct overlay_changeset *ovcs,
return -ENOMEM;
if (!prop) {
- if (!target->in_livetree) {
+ ret = of_changeset_add_property(&ovcs->cset, target->np,
+ new_prop);
+ /* the detached node owns the property until the apply */
+ if (!ret && !target->in_livetree) {
new_prop->next = target->np->deadprops;
target->np->deadprops = new_prop;
}
- ret = of_changeset_add_property(&ovcs->cset, target->np,
- new_prop);
} else {
ret = of_changeset_update_property(&ovcs->cset, target->np,
new_prop);
--
2.54.0
^ permalink raw reply related [flat|nested] 16+ messages in thread* [PATCH v5 5/9] of/overlay: don't keep a negative id in ovcs->id on idr_alloc() failure
2026-07-23 3:19 [PATCH v5 0/9] of: teach overlay code to keep /aliases in sync Abdurrahman Hussain
` (3 preceding siblings ...)
2026-07-23 3:19 ` [PATCH v5 4/9] of/overlay: put property on deadprops only after changeset add succeeds Abdurrahman Hussain
@ 2026-07-23 3:19 ` Abdurrahman Hussain
2026-07-23 3:39 ` sashiko-bot
2026-07-23 3:19 ` [PATCH v5 6/9] of/overlay: don't create "//" paths for fragments targeting the root Abdurrahman Hussain
` (3 subsequent siblings)
8 siblings, 1 reply; 16+ messages in thread
From: Abdurrahman Hussain @ 2026-07-23 3:19 UTC (permalink / raw)
To: Rob Herring, Saravana Kannan, Frank Rowand
Cc: devicetree, linux-kernel, Abdurrahman Hussain
of_overlay_fdt_apply() stores the idr_alloc() return value in
ovcs->id before checking it. On failure the stored id is negative and
the error path runs free_overlay_changeset(), whose "if (ovcs->id)"
check passes: idr_remove() is called with a negative id and
list_del() runs on ovcs->ovcs_list, which is not initialized until
after the id allocation. An allocation failure at that point
dereferences NULL.
Reset ovcs->id to 0 before taking the error path.
Fixes: 61b4de4e0b38 ("of: overlay: minor restructuring")
Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
drivers/of/overlay.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index 284c9bc6c9cf..f1aa8574069a 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -1038,6 +1038,8 @@ int of_overlay_fdt_apply(const void *overlay_fdt, u32 overlay_fdt_size,
ovcs->id = idr_alloc(&ovcs_idr, ovcs, 1, 0, GFP_KERNEL);
if (ovcs->id <= 0) {
ret = ovcs->id;
+ /* free_overlay_changeset() treats a set id as registered */
+ ovcs->id = 0;
goto err_free_ovcs;
}
--
2.54.0
^ permalink raw reply related [flat|nested] 16+ messages in thread* Re: [PATCH v5 5/9] of/overlay: don't keep a negative id in ovcs->id on idr_alloc() failure
2026-07-23 3:19 ` [PATCH v5 5/9] of/overlay: don't keep a negative id in ovcs->id on idr_alloc() failure Abdurrahman Hussain
@ 2026-07-23 3:39 ` sashiko-bot
0 siblings, 0 replies; 16+ messages in thread
From: sashiko-bot @ 2026-07-23 3:39 UTC (permalink / raw)
To: Abdurrahman Hussain; +Cc: devicetree, robh, conor+dt
Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
Pre-existing issues:
- [High] This problem wasn't introduced by this patch, but callers of `of_overlay_fdt_apply()` fail to call `of_overlay_remove()` when the application fails, leading to a memory leak.
- [High] This problem wasn't introduced by this patch, but if `of_changeset_attach_node()` fails in `add_changeset_node()`, the newly allocated device node `tchild` is permanently leaked.
- [High] This problem wasn't introduced by this patch, but if `init_overlay_changeset()` fails after successfully parsing one or more fragments, the OF node references for those initialized fragments are leaked.
--
--- Patch [5]: [PATCH v5 5/9] of/overlay: don't keep a negative id in ovcs->id on idr_alloc() failure ---
commit bdff881a51ac56990164b0a5479bf6e47e64305a
Author: Abdurrahman Hussain <abdurrahman@nexthop.ai>
of/overlay: don't keep a negative id in ovcs->id on idr_alloc() failure
This commit fixes a bug where a negative return value from idr_alloc()
is stored in ovcs->id. On the error path, free_overlay_changeset() checks
if ovcs->id is non-zero, leading to idr_remove() being called with a
negative id and list_del() operating on an uninitialized list.
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index 284c9bc6c9cfc..f1aa8574069a6 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -1038,6 +1038,8 @@ int of_overlay_fdt_apply(const void *overlay_fdt, u32 overlay_fdt_size,
> ovcs->id = idr_alloc(&ovcs_idr, ovcs, 1, 0, GFP_KERNEL);
> if (ovcs->id <= 0) {
> ret = ovcs->id;
> + /* free_overlay_changeset() treats a set id as registered */
> + ovcs->id = 0;
> goto err_free_ovcs;
> }
[Severity: High]
This isn't a bug introduced by this patch, but callers of
of_overlay_fdt_apply() fail to call of_overlay_remove() when the
application fails, leading to a memory leak.
If of_overlay_apply() fails inside of_overlay_fdt_apply(), the function
intentionally leaves the returned changeset ID set via the pointer,
expecting the caller to handle cleanup by calling of_overlay_remove().
However, callers simply return the error code upon failure without
calling of_overlay_remove().
For example, in tilcdc_panel_legacy_probe():
drivers/gpu/drm/tilcdc/tilcdc_panel_legacy.c:tilcdc_panel_legacy_probe() {
...
ret = of_overlay_fdt_apply(dtbo_start, dtbo_size, &ovcs_id, NULL);
if (ret)
return ret;
...
}
And in lan966x_pci_probe():
drivers/misc/lan966x_pci.c:lan966x_pci_probe() {
...
ret = lan966x_pci_load_overlay(data);
if (ret)
return ret;
...
}
The helper returns the result directly to lan966x_pci_probe(), which bails
on error without invoking the corresponding lan966x_pci_unload_overlay().
Can this result in a permanent memory and ID leak of the overlay changeset,
especially since probe functions can be repeatedly triggered via sysfs
bind/unbind or deferred probing?
[Severity: High]
This isn't a bug introduced by this patch, but if of_changeset_attach_node()
fails in add_changeset_node(), is the newly allocated device node
permanently leaked?
In add_changeset_node(), __of_node_dup() creates a new node (tchild) with a
reference count of 1:
drivers/of/overlay.c:add_changeset_node() {
...
ret = of_changeset_attach_node(&ovcs->cset, tchild);
if (ret)
return ret;
...
}
If of_changeset_attach_node() fails, the function returns the error
immediately without dropping the reference to tchild via of_node_put().
Could this leak the device node structure and its associated name string?
[Severity: High]
This isn't a bug introduced by this patch, but if init_overlay_changeset()
fails after successfully parsing one or more fragments, are the OF node
references for those initialized fragments leaked?
In init_overlay_changeset(), the function iterates over overlay fragments
and acquires references via of_get_child_by_name() and find_target(). If
find_target() fails for a subsequent fragment, it jumps to err_out without
dropping the current overlay_node reference or updating ovcs->count:
drivers/of/overlay.c:init_overlay_changeset() {
...
fragment->target = find_target(node, target_base);
if (!fragment->target) {
of_node_put(node);
ret = -EINVAL;
goto err_out;
}
...
}
Because ovcs->count remains 0, free_overlay_changeset() skips the cleanup
loop entirely:
drivers/of/overlay.c:free_overlay_changeset() {
...
for (i = 0; i < ovcs->count; i++) {
of_node_put(ovcs->fragments[i].target);
of_node_put(ovcs->fragments[i].overlay);
}
...
}
Could this skip cleanup and leak the successfully acquired OF nodes from
previous iterations?
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260722-nh-of-alias-overlay-v5-0-2abe2bb9cdbc@nexthop.ai?part=5
^ permalink raw reply [flat|nested] 16+ messages in thread
* [PATCH v5 6/9] of/overlay: don't create "//" paths for fragments targeting the root
2026-07-23 3:19 [PATCH v5 0/9] of: teach overlay code to keep /aliases in sync Abdurrahman Hussain
` (4 preceding siblings ...)
2026-07-23 3:19 ` [PATCH v5 5/9] of/overlay: don't keep a negative id in ovcs->id on idr_alloc() failure Abdurrahman Hussain
@ 2026-07-23 3:19 ` Abdurrahman Hussain
2026-07-23 3:35 ` sashiko-bot
2026-07-23 3:19 ` [PATCH v5 7/9] of/overlay: return ERR_PTR from dup_and_fixup_symbol_prop() Abdurrahman Hussain
` (2 subsequent siblings)
8 siblings, 1 reply; 16+ messages in thread
From: Abdurrahman Hussain @ 2026-07-23 3:19 UTC (permalink / raw)
To: Rob Herring, Saravana Kannan, Frank Rowand
Cc: devicetree, linux-kernel, Abdurrahman Hussain
dup_and_fixup_symbol_prop() rewrites a symbol value by replacing its
"/fragment/__overlay__" prefix with the fragment's target path. When
the fragment targets the root node the target path is "/" and the
result starts with "//", which __of_find_node_by_full_path() cannot
resolve: symbols pointing into such fragments silently stop
resolving.
Drop the target path when it is the root.
Fixes: d1651b03c2df ("of: overlay: add overlay symbols to live device tree")
Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
drivers/of/overlay.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index f1aa8574069a..c6962e9948cc 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -256,6 +256,9 @@ static struct property *dup_and_fixup_symbol_prop(
if (!target_path)
return NULL;
target_path_len = strlen(target_path);
+ /* a root target renders as "/"; drop it to avoid "//" results */
+ if (target_path_len == 1 && target_path[0] == '/')
+ target_path_len = 0;
new_prop = kzalloc_obj(*new_prop);
if (!new_prop)
--
2.54.0
^ permalink raw reply related [flat|nested] 16+ messages in thread* Re: [PATCH v5 6/9] of/overlay: don't create "//" paths for fragments targeting the root
2026-07-23 3:19 ` [PATCH v5 6/9] of/overlay: don't create "//" paths for fragments targeting the root Abdurrahman Hussain
@ 2026-07-23 3:35 ` sashiko-bot
2026-07-23 17:07 ` Abdurrahman Hussain
0 siblings, 1 reply; 16+ messages in thread
From: sashiko-bot @ 2026-07-23 3:35 UTC (permalink / raw)
To: Abdurrahman Hussain; +Cc: conor+dt, robh, devicetree
Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
New issues:
- [Medium] Unconditionally dropping the "/" target path generates an invalid empty string "" for symbols referencing the root of a root-targeted overlay fragment.
Pre-existing issues:
- [Medium] Device node reference count leak in init_overlay_changeset() on error path.
- [Medium] Memory and reference count leak of duplicated device node in add_changeset_node().
--
--- Patch [6]: [PATCH v5 6/9] of/overlay: don't create "//" paths for fragments targeting the root ---
commit aa0fca741484513e2136984fcef43c90b2ab9e9a
Author: Abdurrahman Hussain <abdurrahman@nexthop.ai>
of/overlay: don't create "//" paths for fragments targeting the root
dup_and_fixup_symbol_prop() rewrites a symbol value by replacing its
"/fragment/__overlay__" prefix with the fragment's target path. When
the fragment targets the root node the target path is "/" and the
result starts with "//", which __of_find_node_by_full_path() cannot
resolve: symbols pointing into such fragments silently stop
resolving.
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index f1aa8574069a6..c6962e9948cc9 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -256,6 +256,9 @@ static struct property *dup_and_fixup_symbol_prop(
> if (!target_path)
> return NULL;
> target_path_len = strlen(target_path);
> + /* a root target renders as "/"; drop it to avoid "//" results */
> + if (target_path_len == 1 && target_path[0] == '/')
> + target_path_len = 0;
>
> new_prop = kzalloc_obj(*new_prop);
> if (!new_prop)
[Severity: Medium]
When path_tail_len is 0 (i.e. a symbol referencing the root of a root-targeted
overlay fragment), wouldn't unconditionally clearing target_path_len result in
an empty string "" instead of a valid path?
If path_tail is empty, should we preserve the root "/" target?
[Severity: Medium]
This is a pre-existing issue, but does this error path in
init_overlay_changeset() leak the successfully initialized fragment references?
drivers/of/overlay.c:init_overlay_changeset() {
...
fragment->target = find_target(node, target_base);
if (!fragment->target) {
of_node_put(fragment->overlay);
ret = -EINVAL;
of_node_put(node);
goto err_out;
}
...
}
If a later fragment fails to find its target, the function jumps to err_out
without saving the processed fragment count to ovcs->count. As a result,
free_overlay_changeset() will skip cleaning up the leaked nodes.
[Severity: Medium]
This is a pre-existing issue, but is it possible for add_changeset_node() to
leak the dynamically allocated tchild device node on attachment failure?
drivers/of/overlay.c:add_changeset_node() {
...
if (!tchild) {
tchild = __of_node_dup(NULL, node_kbasename);
...
ret = of_changeset_attach_node(&ovcs->cset, tchild);
if (ret)
return ret;
...
}
When of_changeset_attach_node() fails, it returns directly, skipping the
necessary of_node_put(tchild) call and leaking the node.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260722-nh-of-alias-overlay-v5-0-2abe2bb9cdbc@nexthop.ai?part=6
^ permalink raw reply [flat|nested] 16+ messages in thread* Re: [PATCH v5 6/9] of/overlay: don't create "//" paths for fragments targeting the root
2026-07-23 3:35 ` sashiko-bot
@ 2026-07-23 17:07 ` Abdurrahman Hussain
0 siblings, 0 replies; 16+ messages in thread
From: Abdurrahman Hussain @ 2026-07-23 17:07 UTC (permalink / raw)
To: sashiko-reviews; +Cc: robh, saravanak, frowand.list, devicetree, linux-kernel
On Tue Jul 22, 2026 at 8:35 PM PDT, sashiko-bot wrote:
> [Severity: Medium]
> When path_tail_len is 0 (i.e. a symbol referencing the root of a
> root-targeted overlay fragment), wouldn't unconditionally clearing
> target_path_len result in an invalid empty string "" instead of a valid
> path?
>
> If path_tail is empty, should we preserve the root "/" target?
Right, a symbol for the __overlay__ node itself of a root-targeted
fragment would come out empty instead of "/". The next revision keeps
the target path when the tail is empty:
if (target_path_len == 1 && target_path[0] == '/' && path_tail_len)
target_path_len = 0;
The other two findings are pre-existing and tracked in the cover
letter's open items.
Thanks,
Abdurrahman
^ permalink raw reply [flat|nested] 16+ messages in thread
* [PATCH v5 7/9] of/overlay: return ERR_PTR from dup_and_fixup_symbol_prop()
2026-07-23 3:19 [PATCH v5 0/9] of: teach overlay code to keep /aliases in sync Abdurrahman Hussain
` (5 preceding siblings ...)
2026-07-23 3:19 ` [PATCH v5 6/9] of/overlay: don't create "//" paths for fragments targeting the root Abdurrahman Hussain
@ 2026-07-23 3:19 ` Abdurrahman Hussain
2026-07-23 3:19 ` [PATCH v5 8/9] of/overlay: rewrite /aliases path values to live-tree paths Abdurrahman Hussain
2026-07-23 3:19 ` [PATCH v5 9/9] of: unittest: cover /aliases updates from overlay apply/revert Abdurrahman Hussain
8 siblings, 0 replies; 16+ messages in thread
From: Abdurrahman Hussain @ 2026-07-23 3:19 UTC (permalink / raw)
To: Rob Herring, Saravana Kannan, Frank Rowand
Cc: devicetree, linux-kernel, Abdurrahman Hussain
dup_and_fixup_symbol_prop() returns NULL for malformed values, for
values that are not paths into one of the overlay's fragments, and
for allocation failures. The caller reports all of them as -ENOMEM,
so a structural problem in /__symbols__ is diagnosed as memory
exhaustion.
A later patch reuses the helper for /aliases values and must handle
the three cases differently: copy verbatim, warn, or fail the apply.
Return ERR_PTR(-EINVAL), ERR_PTR(-ENODEV) and ERR_PTR(-ENOMEM)
respectively and propagate the errno in the /__symbols__ caller.
Also verify that the value descends through the matched fragment's
__overlay__ node before cutting the prefix. Only the first path
component was resolved, so an absolute live-tree value sharing its
first component with a fragment name was sliced at the prefix length
and rewritten to garbage. A prefix mismatch returns -ENODEV.
Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
drivers/of/overlay.c | 35 ++++++++++++++++++++++++++---------
1 file changed, 26 insertions(+), 9 deletions(-)
diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index c6962e9948cc..1a2df83fbd8d 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -206,6 +206,10 @@ static void overlay_fw_devlink_refresh(struct overlay_changeset *ovcs)
* The duplicated property value will be modified by replacing the
* "/fragment_name/__overlay/" portion of the value with the target
* path from the fragment node.
+ *
+ * Return: the fixed-up property, or ERR_PTR: -EINVAL if @prop's value
+ * is not a valid non-empty C string, -ENODEV if it is not a path into
+ * one of @ovcs's fragments, -ENOMEM on allocation failure.
*/
static struct property *dup_and_fixup_symbol_prop(
struct overlay_changeset *ovcs, const struct property *prop)
@@ -217,6 +221,8 @@ static struct property *dup_and_fixup_symbol_prop(
const char *path;
const char *path_tail;
const char *target_path;
+ char *overlay_name;
+ bool mismatch;
int k;
int overlay_name_len;
int path_len;
@@ -224,14 +230,14 @@ static struct property *dup_and_fixup_symbol_prop(
int target_path_len;
if (!prop->value)
- return NULL;
+ return ERR_PTR(-EINVAL);
if (strnlen(prop->value, prop->length) >= prop->length)
- return NULL;
+ return ERR_PTR(-EINVAL);
path = prop->value;
path_len = strlen(path);
if (path_len < 1)
- return NULL;
+ return ERR_PTR(-EINVAL);
fragment_node = __of_find_node_by_path(ovcs->overlay_root, path + 1);
overlay_node = __of_find_node_by_path(fragment_node, "__overlay__/");
of_node_put(fragment_node);
@@ -243,18 +249,27 @@ static struct property *dup_and_fixup_symbol_prop(
break;
}
if (k >= ovcs->count)
- return NULL;
+ return ERR_PTR(-ENODEV);
+
+ overlay_name = kasprintf(GFP_KERNEL, "%pOF", fragment->overlay);
+ if (!overlay_name)
+ return ERR_PTR(-ENOMEM);
+ overlay_name_len = strlen(overlay_name);
- overlay_name_len = snprintf(NULL, 0, "%pOF", fragment->overlay);
+ /* @path must descend through this fragment's __overlay__ node */
+ mismatch = overlay_name_len > path_len ||
+ strncmp(path, overlay_name, overlay_name_len) != 0 ||
+ (path[overlay_name_len] != '/' && path[overlay_name_len]);
+ kfree(overlay_name);
+ if (mismatch)
+ return ERR_PTR(-ENODEV);
- if (overlay_name_len > path_len)
- return NULL;
path_tail = path + overlay_name_len;
path_tail_len = strlen(path_tail);
target_path = kasprintf(GFP_KERNEL, "%pOF", fragment->target);
if (!target_path)
- return NULL;
+ return ERR_PTR(-ENOMEM);
target_path_len = strlen(target_path);
/* a root target renders as "/"; drop it to avoid "//" results */
if (target_path_len == 1 && target_path[0] == '/')
@@ -284,7 +299,7 @@ static struct property *dup_and_fixup_symbol_prop(
err_free_target_path:
kfree(target_path);
- return NULL;
+ return ERR_PTR(-ENOMEM);
}
/**
@@ -353,6 +368,8 @@ static int add_changeset_property(struct overlay_changeset *ovcs,
if (prop)
return -EINVAL;
new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
+ if (IS_ERR(new_prop))
+ return PTR_ERR(new_prop);
} else {
new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
}
--
2.54.0
^ permalink raw reply related [flat|nested] 16+ messages in thread* [PATCH v5 8/9] of/overlay: rewrite /aliases path values to live-tree paths
2026-07-23 3:19 [PATCH v5 0/9] of: teach overlay code to keep /aliases in sync Abdurrahman Hussain
` (6 preceding siblings ...)
2026-07-23 3:19 ` [PATCH v5 7/9] of/overlay: return ERR_PTR from dup_and_fixup_symbol_prop() Abdurrahman Hussain
@ 2026-07-23 3:19 ` Abdurrahman Hussain
2026-07-23 3:19 ` [PATCH v5 9/9] of: unittest: cover /aliases updates from overlay apply/revert Abdurrahman Hussain
8 siblings, 0 replies; 16+ messages in thread
From: Abdurrahman Hussain @ 2026-07-23 3:19 UTC (permalink / raw)
To: Rob Herring, Saravana Kannan, Frank Rowand
Cc: devicetree, linux-kernel, Abdurrahman Hussain
An /aliases property added by an overlay references labeled nodes as
"&label", which dtc renders as an overlay-internal path such as
"/fragment@1/__overlay__/i2c@40000". The value is copied verbatim
into the live tree, of_find_node_by_path() cannot resolve it, and
of_alias_get_id() keeps returning -ENODEV.
/__symbols__ values follow the same convention and are already
rewritten by dup_and_fixup_symbol_prop(). Use it for properties of
the /aliases node too:
- a value that resolves inside one of the overlay's fragments is
stored rewritten to the live-tree path
- -ENODEV (legacy string aliases, absolute live-tree paths) is
copied verbatim, as before this series
- -EINVAL (not a NUL-terminated string) is copied verbatim with a
warning; consumers validate before dereferencing, and an overlay
that applied before this series keeps applying
- only -ENOMEM fails the apply
Pseudo-properties are exempt: the is_pseudo_property() check at the
top of add_changeset_property() only covers live-tree targets, and a
phandle of a newly created /aliases node is a cell, not a string.
Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
drivers/of/overlay.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index 1a2df83fbd8d..27a460daeed9 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -370,6 +370,19 @@ static int add_changeset_property(struct overlay_changeset *ovcs,
new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
if (IS_ERR(new_prop))
return PTR_ERR(new_prop);
+ } else if (!is_pseudo_property(overlay_prop->name) &&
+ of_node_is_aliases(target->np)) {
+ /* rewrite overlay-internal alias values to live-tree paths */
+ new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
+ if (new_prop == ERR_PTR(-ENOMEM))
+ return -ENOMEM;
+ if (IS_ERR(new_prop)) {
+ if (new_prop == ERR_PTR(-EINVAL))
+ pr_warn("%pOF/%s is not a valid string; alias will be inert\n",
+ target->np, overlay_prop->name);
+ /* not overlay-internal: copy verbatim, consumers validate */
+ new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
+ }
} else {
new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
}
--
2.54.0
^ permalink raw reply related [flat|nested] 16+ messages in thread* [PATCH v5 9/9] of: unittest: cover /aliases updates from overlay apply/revert
2026-07-23 3:19 [PATCH v5 0/9] of: teach overlay code to keep /aliases in sync Abdurrahman Hussain
` (7 preceding siblings ...)
2026-07-23 3:19 ` [PATCH v5 8/9] of/overlay: rewrite /aliases path values to live-tree paths Abdurrahman Hussain
@ 2026-07-23 3:19 ` Abdurrahman Hussain
8 siblings, 0 replies; 16+ messages in thread
From: Abdurrahman Hussain @ 2026-07-23 3:19 UTC (permalink / raw)
To: Rob Herring, Saravana Kannan, Frank Rowand
Cc: devicetree, linux-kernel, Abdurrahman Hussain
Add overlay_alias.dtso and of_unittest_overlay_alias().
The overlay has two fragments: target-path="" grafts a labeled node
under the run-time target base, and target-path="/aliases" adds
`testcase-alias99 = &<label>` at the DT root. The runner applies it
with a non-NULL base via of_overlay_fdt_apply() (overlay_data_apply()
always passes NULL), asserts of_alias_get_id() on the grafted node
returns 99, reverts, and asserts of_alias_get_highest_id() reports
the stem gone. A precondition check runs before the apply.
This exercises the reconfig notifier, the absolute target-path
lookup, and the /aliases value rewrite together; any one missing
turns the get_id assertion into -ENODEV.
The grafted-node reference is dropped before of_overlay_remove():
overlay-created nodes must be back at refcount 1 when the changeset
is destroyed. The post-remove assertion uses of_alias_get_highest_id()
because it is keyed by stem and needs no node reference. The apply is
wrapped in EXPECT_BEGIN/END for the "memory leak will occur" warning
printed for properties added to nodes the overlay didn't create,
like the other overlay tests.
The overlay is not added to the fdtoverlay static build test:
fdtoverlay has no target-base concept, so the empty target-path
cannot be resolved statically.
Assisted-by: Claude:claude-fable-5 [Claude Code]
Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
---
drivers/of/unittest-data/Makefile | 5 ++
drivers/of/unittest-data/overlay_alias.dtso | 25 ++++++++++
drivers/of/unittest.c | 73 +++++++++++++++++++++++++++++
3 files changed, 103 insertions(+)
diff --git a/drivers/of/unittest-data/Makefile b/drivers/of/unittest-data/Makefile
index 01a966e39f23..fdfec5a7923b 100644
--- a/drivers/of/unittest-data/Makefile
+++ b/drivers/of/unittest-data/Makefile
@@ -22,6 +22,7 @@ obj-$(CONFIG_OF_OVERLAY) += overlay.dtbo.o \
overlay_18.dtbo.o \
overlay_19.dtbo.o \
overlay_20.dtbo.o \
+ overlay_alias.dtbo.o \
overlay_bad_add_dup_node.dtbo.o \
overlay_bad_add_dup_prop.dtbo.o \
overlay_bad_phandle.dtbo.o \
@@ -66,6 +67,10 @@ DTC_FLAGS_testcases += -Wno-interrupts_property \
# overlay_bad_add_dup_prop.dtbo \
# overlay_bad_phandle.dtbo \
# overlay_bad_symbol.dtbo \
+#
+# overlay_alias.dtbo needs a run-time target base for its empty target-path;
+# fdtoverlay has no equivalent, so it is also not included:
+# overlay_alias.dtbo \
apply_static_overlay_1 := overlay_0.dtbo \
overlay_1.dtbo \
diff --git a/drivers/of/unittest-data/overlay_alias.dtso b/drivers/of/unittest-data/overlay_alias.dtso
new file mode 100644
index 000000000000..17e02d1940f6
--- /dev/null
+++ b/drivers/of/unittest-data/overlay_alias.dtso
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/dts-v1/;
+/plugin/;
+
+/*
+ * overlay_alias - declare an /aliases entry that points, via label, at a
+ * node grafted under the run-time target base (empty target-path).
+ */
+
+/ {
+ fragment@0 {
+ target-path = "";
+ __overlay__ {
+ testcase_target: alias-target {
+ };
+ };
+ };
+
+ fragment@1 {
+ target-path = "/aliases";
+ __overlay__ {
+ testcase-alias99 = &testcase_target;
+ };
+ };
+};
diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
index e255f54f4d76..2f5e4056efae 100644
--- a/drivers/of/unittest.c
+++ b/drivers/of/unittest.c
@@ -3475,6 +3475,77 @@ static struct notifier_block of_nb = {
.notifier_call = of_notify,
};
+/* created by cmd_wrap_S_dtbo in scripts/Makefile.dtbs */
+extern uint8_t __dtbo_overlay_alias_begin[];
+extern uint8_t __dtbo_overlay_alias_end[];
+
+static void __init of_unittest_overlay_alias(void)
+{
+ const char *base_path =
+ "/testcase-data/overlay-node/test-bus/test-unittest100";
+ const char *target_path =
+ "/testcase-data/overlay-node/test-bus/test-unittest100/alias-target";
+ u32 size = __dtbo_overlay_alias_end - __dtbo_overlay_alias_begin;
+ struct device_node *base, *target;
+ int ovcs_id = 0;
+ int id, ret;
+
+ base = of_find_node_by_path(base_path);
+ if (!base) {
+ unittest(0, "could not find alias target base %s\n", base_path);
+ return;
+ }
+
+ id = of_alias_get_highest_id("testcase-alias");
+ if (id != -ENODEV) {
+ unittest(0, "unexpected testcase-alias%d before overlay apply\n",
+ id);
+ goto out_put_base;
+ }
+
+ EXPECT_BEGIN(KERN_INFO,
+ "OF: overlay: WARNING: memory leak will occur if overlay removed, property: /aliases/testcase-alias99");
+
+ ret = of_overlay_fdt_apply(__dtbo_overlay_alias_begin, size,
+ &ovcs_id, base);
+
+ EXPECT_END(KERN_INFO,
+ "OF: overlay: WARNING: memory leak will occur if overlay removed, property: /aliases/testcase-alias99");
+
+ if (ret < 0) {
+ unittest(0, "overlay_alias apply failed, ret = %d\n", ret);
+ if (ovcs_id)
+ of_overlay_remove(&ovcs_id);
+ goto out_put_base;
+ }
+
+ target = of_find_node_by_path(target_path);
+ if (!target) {
+ unittest(0, "could not find grafted target %s\n", target_path);
+ } else {
+ id = of_alias_get_id(target, "testcase-alias");
+ unittest(id == 99,
+ "of_alias_get_id() = %d after overlay apply, expected 99\n",
+ id);
+ /* changeset destroy expects overlay nodes back at refcount 1 */
+ of_node_put(target);
+ }
+
+ ret = of_overlay_remove(&ovcs_id);
+ if (ret) {
+ unittest(0, "overlay_alias remove failed, ret = %d\n", ret);
+ goto out_put_base;
+ }
+
+ id = of_alias_get_highest_id("testcase-alias");
+ unittest(id == -ENODEV,
+ "of_alias_get_highest_id() = %d after overlay remove, expected -ENODEV\n",
+ id);
+
+out_put_base:
+ of_node_put(base);
+}
+
static void __init of_unittest_overlay_notify(void)
{
int ovcs_id;
@@ -3649,6 +3720,8 @@ static void __init of_unittest_overlay(void)
of_unittest_overlay_gpio();
+ of_unittest_overlay_alias();
+
of_unittest_remove_tracked_overlays();
of_unittest_overlay_notify();
--
2.54.0
^ permalink raw reply related [flat|nested] 16+ messages in thread