Re: [PATCH 5/5] sysctl: pass kernel pointers to ->proc_handler
From: Al Viro <viro@zeniv.linux.org.uk>
Date: 2020-04-21 19:16:30
Also in:
bpf, linux-fsdevel, linux-mm, lkml
On Tue, Apr 21, 2020 at 07:15:39PM +0200, Christoph Hellwig wrote:
Instead of having all the sysctl handlers deal with user pointers, which is rather hairy in terms of the BPF interaction, copy the input to and from userspace in common code. This also means that the strings are always NUL-terminated by the common code, making the API a little bit safer. As most handler just pass through the data to one of the common handlers a lot of the changes are mechnical.
quoted hunk ↗ jump to hunk
@@ -564,27 +564,38 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf, if (!table->proc_handler) goto out; - error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, buf, &count, - ppos, &new_buf); + if (write) { + kbuf = memdup_user_nul(ubuf, count); + if (IS_ERR(kbuf)) { + error = PTR_ERR(kbuf); + goto out; + } + } else { + error = -ENOMEM; + kbuf = kzalloc(count, GFP_KERNEL);
Better allocate count + 1 bytes here, that way a lot of insanity in the instances can be simply converted to snprintf(). Yes, I know it'll bring the Church Of Avoiding The Abomination Of Sprintf out of the woodwork, but...