[PATCH v2 2/2] staging/lustre/llite: fix ll_getname user buffer copy

From: green
Date: Thu Jun 11 2015 - 01:38:42 EST


From: Oleg Drokin <green@xxxxxxxxxxxxxx>

strncpy_from_user could return negative values on error,
so need to take those into account.
Since ll_getname is used to get a single component name from userspace
to transfer to server as-is, there's no need to allocate 4k buffer
as done by __getname. Allocate NAME_MAX+1 buffer instead to ensure
we have enough for a null terminated max valid length buffer.

This was discovered by Al Viro in https://lkml.org/lkml/2015/4/11/243

Signed-off-by: Oleg Drokin <green@xxxxxxxxxxxxxx>
---
drivers/staging/lustre/lustre/llite/dir.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/staging/lustre/lustre/llite/dir.c b/drivers/staging/lustre/lustre/llite/dir.c
index 87a042c..50d685b 100644
--- a/drivers/staging/lustre/lustre/llite/dir.c
+++ b/drivers/staging/lustre/lustre/llite/dir.c
@@ -1213,29 +1213,34 @@ out:
return rc;
}

-static char *
-ll_getname(const char __user *filename)
+/* This function tries to get a single name component,
+ * to send to the server. No actual path traversal involved,
+ * so we limit to NAME_MAX */
+static char *ll_getname(const char __user *filename)
{
int ret = 0, len;
- char *tmp = __getname();
+ char *tmp;

+ tmp = kzalloc(NAME_MAX + 1, GFP_KERNEL);
if (!tmp)
return ERR_PTR(-ENOMEM);

- len = strncpy_from_user(tmp, filename, PATH_MAX);
- if (len == 0)
+ len = strncpy_from_user(tmp, filename, NAME_MAX + 1);
+ if (len < 0)
+ ret = len;
+ else if (len == 0)
ret = -ENOENT;
- else if (len > PATH_MAX)
+ else if (len > NAME_MAX && tmp[NAME_MAX] != 0)
ret = -ENAMETOOLONG;

if (ret) {
- __putname(tmp);
+ kfree(tmp);
tmp = ERR_PTR(ret);
}
return tmp;
}

-#define ll_putname(filename) __putname(filename)
+#define ll_putname(filename) kfree(filename)

static long ll_dir_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
--
2.1.0

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