Re: [PATCH v2] tracing/osnoise: Replace kmalloc + copy_from_user with memdup_user
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2025-09-30 21:27:14
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lkml
On Thu, 25 Sep 2025 23:17:36 +0200 Thorsten Blum [off-list ref] wrote:
quoted hunk ↗ jump to hunk
#ifdef CONFIG_X86_LOCAL_APIC@@ -2325,12 +2326,9 @@ osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count, if (count < 1) return 0; - buf = kmalloc(count, GFP_KERNEL); - if (!buf) - return -ENOMEM; - - if (copy_from_user(buf, ubuf, count)) - return -EFAULT; + buf = memdup_user(ubuf, count); + if (IS_ERR(buf)) + return PTR_ERR(buf);
After adding this to my for-next branch, it failed to merge with upstream. That's because a bug was found that if user space did not have a '\0' terminator, reading this as a string could cause the read to go off the allocated buffer and crash the machine.
if (!zalloc_cpumask_var(&osnoise_cpumask_new, GFP_KERNEL)) return -ENOMEM;
The above was changed to this: if (count < 1) return 0; buf = kmalloc(count + 1, GFP_KERNEL); if (!buf) return -ENOMEM; if (copy_from_user(buf, ubuf, count)) return -EFAULT; buf[count] = '\0'; Which makes your change not quite compatible. I'm going to rebase and remove your change for now. -- Steve