Patch "proc: use kvzalloc for our kernel buffer" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    proc: use kvzalloc for our kernel buffer

to the 5.10-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:
     proc-use-kvzalloc-for-our-kernel-buffer.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 8552a2495face6ae049b7f6f05cc48cf1aa6a428
Author: Josef Bacik <josef@xxxxxxxxxxxxxx>
Date:   Thu Feb 25 17:20:49 2021 -0800

    proc: use kvzalloc for our kernel buffer
    
    [ Upstream commit 4508943794efdd94171549c0bd52810e2f4ad9fe ]
    
    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.
    
    [willy@xxxxxxxxxxxxx: changelog tweaks]
    
    Link: https://lkml.kernel.org/r/6345270a2c1160b89dd5e6715461f388176899d1.1612972413.git.josef@xxxxxxxxxxxxxx
    Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")
    Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
    Reviewed-by: Christoph Hellwig <hch@xxxxxx>
    Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
    Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
    Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
    CC: Matthew Wilcox <willy@xxxxxxxxxxxxx>
    Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index d2018f70d1fae..070d2df8ab9cf 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -571,7 +571,7 @@ static ssize_t proc_sys_call_handler(struct kiocb *iocb, struct iov_iter *iter,
 	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(struct kiocb *iocb, struct iov_iter *iter,
 
 	error = count;
 out_free_buf:
-	kfree(kbuf);
+	kvfree(kbuf);
 out:
 	sysctl_head_finish(head);