linux-hardening - Re: [PATCH v2] eventfs: Use kcalloc() instead of kzalloc()

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Date: Mon, 15 Jan 2024 12:24:50 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Erick Archer <erick.archer@....com>, Steven Rostedt
 <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Mark Rutland <mark.rutland@....com>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] eventfs: Use kcalloc() instead of kzalloc()



On 1/15/24 12:16, Erick Archer wrote:
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
> 
> So, use the purpose specific kcalloc() function instead of the argument
> size * count in the kzalloc() function.
> 
> [1] https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> 
> Link: https://github.com/KSPP/linux/issues/162
> Signed-off-by: Erick Archer <erick.archer@....com>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks!
-- 
Gustavo

> ---
> Changes in v2:
> - Update the commit message to better explain the changes (Mark Rutland)
> 
> Previous versions:
> v1: https://lore.kernel.org/linux-hardening/20240114105340.5746-1-erick.archer@gmx.com/
> ---
>   fs/tracefs/event_inode.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
> index fdff53d5a1f8..f8196289692c 100644
> --- a/fs/tracefs/event_inode.c
> +++ b/fs/tracefs/event_inode.c
> @@ -93,7 +93,7 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
>   	/* Preallocate the children mode array if necessary */
>   	if (!(dentry->d_inode->i_mode & S_IFDIR)) {
>   		if (!ei->entry_attrs) {
> -			ei->entry_attrs = kzalloc(sizeof(*ei->entry_attrs) * ei->nr_entries,
> +			ei->entry_attrs = kcalloc(ei->nr_entries, sizeof(*ei->entry_attrs),
>   						  GFP_NOFS);
>   			if (!ei->entry_attrs) {
>   				ret = -ENOMEM;
> @@ -874,7 +874,7 @@ struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode
>   	}
> 
>   	if (size) {
> -		ei->d_children = kzalloc(sizeof(*ei->d_children) * size, GFP_KERNEL);
> +		ei->d_children = kcalloc(size, sizeof(*ei->d_children), GFP_KERNEL);
>   		if (!ei->d_children) {
>   			kfree_const(ei->name);
>   			kfree(ei);
> @@ -941,7 +941,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
>   		goto fail;
> 
>   	if (size) {
> -		ei->d_children = kzalloc(sizeof(*ei->d_children) * size, GFP_KERNEL);
> +		ei->d_children = kcalloc(size, sizeof(*ei->d_children), GFP_KERNEL);
>   		if (!ei->d_children)
>   			goto fail;
>   	}
> --
> 2.25.1
> 
>