[PATCH v2 05/10] mm/util: Fix possible race condition in kstrdup()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



In kstrdup(), it is critical to ensure that the dest string is always
NUL-terminated. However, potential race condidtion can occur between a
writer and a reader.

Consider the following scenario involving task->comm:

    reader                    writer

  len = strlen(s) + 1;
                             strlcpy(tsk->comm, buf, sizeof(tsk->comm));
  memcpy(buf, s, len);

In this case, there is a race condition between the reader and the
writer. The reader calculate the length of the string `s` based on the
old value of task->comm. However, during the memcpy(), the string `s`
might be updated by the writer to a new value of task->comm.

If the new task->comm is larger than the old one, the `buf` might not be
NUL-terminated. This can lead to undefined behavior and potential
security vulnerabilities.

Let's fix it by explicitly adding a NUL-terminator.

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 mm/util.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/util.c b/mm/util.c
index c9e519e6811f..3b383f790208 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -60,8 +60,10 @@ char *kstrdup(const char *s, gfp_t gfp)
 
 	len = strlen(s) + 1;
 	buf = kmalloc_track_caller(len, gfp);
-	if (buf)
+	if (buf) {
 		memcpy(buf, s, len);
+		buf[len - 1] = '\0';
+	}
 	return buf;
 }
 EXPORT_SYMBOL(kstrdup);
-- 
2.39.1





[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [NTFS 3]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [NTFS 3]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux