linux-kernel - [PATCH] mm/slab: make __free(kfree) accept error pointers

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Date: Sun, 28 Apr 2024 17:26:44 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Christoph Lameter <cl@...ux.com>, Peter Zijlstra <peterz@...radead.org>
Cc: Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH] mm/slab: make __free(kfree) accept error pointers

Currently, if an automatically freed allocation is an error pointer that
will lead to a crash.  An example of this is in wm831x_gpio_dbg_show().

   171	char *label __free(kfree) = gpiochip_dup_line_label(chip, i);
   172	if (IS_ERR(label)) {
   173		dev_err(wm831x->dev, "Failed to duplicate label\n");
   174		continue;
   175  }

The auto clean up function should check for error pointers as well,
otherwise we're going to keep hitting issues like this.

Fixes: 54da6a092431 ("locking: Introduce __cleanup() based infrastructure")
Cc: <stable@...r.kernel.org>
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
Obviously, the fixes tag isn't very fair but it will tell the -stable
tools how far to backport this.

 include/linux/slab.h  | 4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 4cc37ef22aae..5f5766219375 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -279,7 +279,7 @@ void kfree(const void *objp);
 void kfree_sensitive(const void *objp);
 size_t __ksize(const void *objp);
 
-DEFINE_FREE(kfree, void *, if (_T) kfree(_T))
+DEFINE_FREE(kfree, void *, if (!IS_ERR_OR_NULL(_T)) kfree(_T))
 
 /**
  * ksize - Report actual allocation size of associated object
@@ -808,7 +808,7 @@ extern void *kvrealloc_noprof(const void *p, size_t oldsize, size_t newsize, gfp
 #define kvrealloc(...)				alloc_hooks(kvrealloc_noprof(__VA_ARGS__))
 
 extern void kvfree(const void *addr);
-DEFINE_FREE(kvfree, void *, if (_T) kvfree(_T))
+DEFINE_FREE(kvfree, void *, if (!IS_ERR_OR_NULL(_T)) kvfree(_T))
 
 extern void kvfree_sensitive(const void *addr, size_t len);
 
-- 
2.43.0