From: Yicong Yang <yangyicong@xxxxxxxxxxxxx> Subject: 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. Link: https://lkml.kernel.org/r/1605341356-11872-1-git-send-email-yangyicong@xxxxxxxxxxxxx Fixes: f7b88631a897 ("fs/libfs.c: fix simple_attr_write() on 32bit machines") Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/libfs.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/fs/libfs.c~libfs-fix-error-cast-of-negative-value-in-simple_attr_write +++ a/fs/libfs.c @@ -959,7 +959,7 @@ ssize_t simple_attr_write(struct file *f 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 *f 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 */ _
