[084/118] proc: use kvzalloc for our kernel buffer

Commit Message

Andrew Morton Feb. 26, 2021, 1:20 a.m. UTC

From: Josef Bacik <[e-mail]>
Subject: proc: use kvzalloc for our kernel buffer

Since

  sysctl: pass kernel pointers to ->proc_handler

we have been pre-allocating a buffer to copy the data from the proc
handlers into, and then copying that to userspace.  The problem is this
just blindly kzalloc()'s the buffer size passed in from the read, which in
the case of our 'cat' binary was 64kib.  Order-4 allocations are not
awesome, and since we can potentially allocate up to our maximum order, so
use kvzalloc for these buffers.

[[e-mail]: changelog tweaks]
Link: https://lkml.kernel.org/r/[e-mail]
Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")
Signed-off-by: Josef Bacik <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Acked-by: Vlastimil Babka <[e-mail]>
Cc: Al Viro <[e-mail]>
Cc: Alexey Dobriyan <[e-mail]>
CC: Matthew Wilcox <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 fs/proc/proc_sysctl.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Patch

--- a/fs/proc/proc_sysctl.c~proc-use-vmalloc-for-our-kernel-buffer
+++ a/fs/proc/proc_sysctl.c
@@ -571,7 +571,7 @@  static ssize_t proc_sys_call_handler(str
 	error = -ENOMEM;
 	if (count >= KMALLOC_MAX_SIZE)
 		goto out;
-	kbuf = kzalloc(count + 1, GFP_KERNEL);
+	kbuf = kvzalloc(count + 1, GFP_KERNEL);
 	if (!kbuf)
 		goto out;
 
@@ -600,7 +600,7 @@  static ssize_t proc_sys_call_handler(str
 
 	error = count;
 out_free_buf:
-	kfree(kbuf);
+	kvfree(kbuf);
 out:
 	sysctl_head_finish(head);