[PATCH 5.4 112/158] libfs: fix error cast of negative value in simple_attr_write()

Greg Kroah-Hartman
2020-11-23T13:21:28Z

From: Yicong Yang <yangyicong@hisilicon.com>

[ Upstream commit 488dac0c9237647e9b8f788b6a342595bfa40bda ]

The attr->set() receive a value of u64, but simple_strtoll() is used for
doing the conversion. It will lead to the error cast if user inputs a
negative value.

Use kstrtoull() instead of simple_strtoll() to convert a string got from
the user to an unsigned value. The former will return '-EINVAL' if it
gets a negetive value, but the latter can't handle the situation
correctly. Make 'val' unsigned long long as what kstrtoull() takes,
this will eliminate the compile warning on no 64-bit architectures.

Fixes: f7b88631a897 ("fs/libfs.c: fix simple_attr_write() on 32bit machines")
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lkml.kernel.org/r/1605341356-11872-1-git-send-email-yangyicong@hisilicon.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/libfs.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/libfs.c b/fs/libfs.c
index 5fd9cc0e2ac9e..247b58a68240a 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -887,7 +887,7 @@ ssize_t simple_attr_write(struct file *file, const char __user *buf,
size_t len, loff_t *ppos)
{
struct simple_attr *attr;
- u64 val;
+ unsigned long long val;
size_t size;
ssize_t ret;

@@ -905,7 +905,9 @@ ssize_t simple_attr_write(struct file *file, const char __user *buf,
goto out;

attr->set_buf[size] = '\0';
- val = simple_strtoll(attr->set_buf, NULL, 0);
+ ret = kstrtoull(attr->set_buf, 0, &val);
+ if (ret)
+ goto out;
ret = attr->set(attr->data, val);
if (ret == 0)
ret = len; /* on success, claim we got the whole input */
--
2.27.0