This is a note to let you know that I've just added the patch titled libfs: fix error cast of negative value in simple_attr_write() to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: libfs-fix-error-cast-of-negative-value-in-simple_att.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit c3ae1399c26f662ba5a9239d2c6bd8cf44dd9ea5 Author: Yicong Yang <yangyicong@xxxxxxxxxxxxx> Date: Sat Nov 21 22:17:19 2020 -0800 libfs: fix error cast of negative value in simple_attr_write() [ 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@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/1605341356-11872-1-git-send-email-yangyicong@xxxxxxxxxxxxx Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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 */