Commit 488dac0c authored Nov 21, 2020 by Yicong Yang Committed by Linus Torvalds Nov 22, 2020

libfs: fix error cast of negative value in simple_attr_write()

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: f7b88631 ("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>

parent bfe8cc1d

fs/libfs.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -959,7 +959,7 @@ 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;

		@@ -977,7 +977,9 @@ 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 */

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