linux-kernel - [PATCH v2] kobject: return -ENOSPC when add_uevent

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20190610210924.9514-1-yamada.masahiro@socionext.com>
Date:   Tue, 11 Jun 2019 06:09:24 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        linux-kernel@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: [PATCH v2] kobject: return -ENOSPC when add_uevent_var() fails

This function never attempts to allocate memory, so returning -ENOMEM
looks weird to me. The reason of the failure is there is no more space
in the given kobj_uevent_env structure.

Let's change the error code to -ENOSPC.

This patch is safe since this function had never failed in reality.

The callers of this function put a fixed number of small strings into
the buffer.

The buffer is defined to be large enough:

  #define UEVENT_NUM_ENVP                 32      /* number of env pointers */
  #define UEVENT_BUFFER_SIZE              2048    /* buffer for the variables */

As you see WARN() in the error paths, any failure of this function is
a software bug.

If such a case had ever happened before, you would have already seen
a noisy back-trace, then you would have increased UEVENT_NUM_ENVP or
UEVENT_BUFFER_SIZE.

Nobody has ever increased UEVENT_NUM_ENVP or UEVENT_BUFFER_SIZE since
their addition, that is, this structure is always large enough.

Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
---

Changes in v2:
  - Rephrase the commit log. No code change.

 lib/kobject_uevent.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index 7998affa45d4..5ffd44bf4aad 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -647,7 +647,7 @@ EXPORT_SYMBOL_GPL(kobject_uevent);
  * @env: environment buffer structure
  * @format: printf format for the key=value pair
  *
- * Returns 0 if environment variable was added successfully or -ENOMEM
+ * Returns 0 if environment variable was added successfully or -ENOSPC
  * if no space was available.
  */
 int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
@@ -657,7 +657,7 @@ int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
 
 	if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
 		WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
-		return -ENOMEM;
+		return -ENOSPC;
 	}
 
 	va_start(args, format);
@@ -668,7 +668,7 @@ int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
 
 	if (len >= (sizeof(env->buf) - env->buflen)) {
 		WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
-		return -ENOMEM;
+		return -ENOSPC;
 	}
 
 	env->envp[env->envp_idx++] = &env->buf[env->buflen];
-- 
2.17.1