From 32927393dc1ccd60fb2bdc05b9e8e88753761469 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 24 Apr 2020 08:43:38 +0200 Subject: sysctl: pass kernel pointers to ->proc_handler 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. Signed-off-by: Christoph Hellwig Acked-by: Andrey Ignatov Signed-off-by: Al Viro --- fs/proc/proc_sysctl.c | 47 +++++++++++++++++++++++++++++------------------ 1 file changed, 29 insertions(+), 18 deletions(-) (limited to 'fs/proc/proc_sysctl.c') diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index b6f5d459b087..df2143e05c57 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -539,13 +539,13 @@ out: return err; } -static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf, +static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf, size_t count, loff_t *ppos, int write) { struct inode *inode = file_inode(filp); struct ctl_table_header *head = grab_header(inode); struct ctl_table *table = PROC_I(inode)->sysctl_entry; - void *new_buf = NULL; + void *kbuf; ssize_t error; if (IS_ERR(head)) @@ -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); + if (!kbuf) + goto out; + } + + error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count, + ppos); if (error) - goto out; + goto out_free_buf; /* careful: calling conventions are nasty here */ - if (new_buf) { - mm_segment_t old_fs; - - old_fs = get_fs(); - set_fs(KERNEL_DS); - error = table->proc_handler(table, write, (void __user *)new_buf, - &count, ppos); - set_fs(old_fs); - kfree(new_buf); - } else { - error = table->proc_handler(table, write, buf, &count, ppos); + error = table->proc_handler(table, write, kbuf, &count, ppos); + if (error) + goto out_free_buf; + + if (!write) { + error = -EFAULT; + if (copy_to_user(ubuf, kbuf, count)) + goto out_free_buf; } - if (!error) - error = count; + error = count; +out_free_buf: + kfree(kbuf); out: sysctl_head_finish(head); -- cgit v1.2.3