linux-kernel - Re: [PATCH v1 3/3] btrfs: replace kmalloc() and memcpy() with kmemdup()

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Message-ID: <2b4d265c-0efe-43b4-890e-dbab59d9d7b0@meta.com>
Date: Wed, 18 Dec 2024 10:32:36 +0000
From: Mark Harmstone <maharmstone@...a.com>
To: Mirsad Todorovac <mtodorovac69@...il.com>,
        Alex Deucher
	<alexander.deucher@....com>,
        Victor Skvortsov <victor.skvortsov@....com>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: Christian König <christian.koenig@....com>,
        Xinhui
 Pan <Xinhui.Pan@....com>, David Airlie <airlied@...il.com>,
        Simona Vetter
	<simona@...ll.ch>, Chris Mason <clm@...a.com>,
        Josef Bacik
	<josef@...icpanda.com>, David Sterba <dsterba@...e.com>,
        "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>
Subject: Re: [PATCH v1 3/3] btrfs: replace kmalloc() and memcpy() with
 kmemdup()

There's a fix for this already in the for-next branch:
https://github.com/btrfs/linux/commit/1a287050962c6847fa4918d6b2a0f4cee35c6943

On 17/12/24 22:58, Mirsad Todorovac wrote:
> > 
> The static analyser tool gave the following advice:
> 
> ./fs/btrfs/ioctl.c:4987:9-16: WARNING opportunity for kmemdup
> 
>     4986                 if (!iov) {
>   → 4987                         iov = kmalloc(sizeof(struct iovec) * args.iovcnt, GFP_NOFS);
>     4988                         if (!iov) {
>     4989                                 unlock_extent(io_tree, start, lockend, &cached_state);
>     4990                                 btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
>     4991                                 ret = -ENOMEM;
>     4992                                 goto out_acct;
>     4993                         }
>     4994
>   → 4995                         memcpy(iov, iovstack, sizeof(struct iovec) * args.iovcnt);
>     4996                 }
> 
> Replacing kmalloc() + memcpy() with kmemdump() doesn't change semantics.
> Original code works without fault, so this is not a bug fix but proposed improvement.
> 
> Link: https://urldefense.com/v3/__https://lwn.net/Articles/198928/__;!!Bt8RZUm9aw!4OVzQmIUbyH-UGdUwMAL582hR4Q-7HN2fn9IpyxeA1T8qrcC8RdBVz4xuL4m35_kksUllAi6OmdbRehcFpwfHw$
> Fixes: 34310c442e175 ("btrfs: add io_uring command for encoded reads (ENCODED_READ ioctl)")
> Cc: Chris Mason <clm@...com>
> Cc: Josef Bacik <josef@...icpanda.com>
> Cc: David Sterba <dsterba@...e.com>
> Cc: linux-btrfs@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Mirsad Todorovac <mtodorovac69@...il.com>
> ---
>   v1:
> 	initial version.
> 
>   fs/btrfs/ioctl.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 3af8bb0c8d75..c2f769334d3c 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -4984,15 +4984,13 @@ static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue
>   		 * undo this.
>   		 */
>   		if (!iov) {
> -			iov = kmalloc(sizeof(struct iovec) * args.iovcnt, GFP_NOFS);
> +			iov = kmemdup(iovstack, sizeof(struct iovec) * args.iovcnt, GFP_NOFS);
>   			if (!iov) {
>   				unlock_extent(io_tree, start, lockend, &cached_state);
>   				btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
>   				ret = -ENOMEM;
>   				goto out_acct;
>   			}
> -
> -			memcpy(iov, iovstack, sizeof(struct iovec) * args.iovcnt);
>   		}
>   
>   		count = min_t(u64, iov_iter_count(&iter), disk_io_size);