linux-kernel - Re: [RFC PATCH 1/3] fs/pipe: Limit the slots in pipe_resize

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Message-ID: <1c4b7bb2-2b2c-472f-b392-ac75cf482ec0@amd.com>
Date: Thu, 6 Mar 2025 20:56:32 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Oleg Nesterov <oleg@...hat.com>
CC: Linus Torvalds <torvalds@...ux-foundation.org>, Miklos Szeredi
	<miklos@...redi.hu>, Alexander Viro <viro@...iv.linux.org.uk>, "Christian
 Brauner" <brauner@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>,
	"Hugh Dickins" <hughd@...gle.com>, <linux-fsdevel@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>, Jan Kara
	<jack@...e.cz>, "Matthew Wilcox (Oracle)" <willy@...radead.org>, "Mateusz
 Guzik" <mjguzik@...il.com>, "Gautham R. Shenoy" <gautham.shenoy@....com>,
	Rasmus Villemoes <ravi@...vas.dk>, <Neeraj.Upadhyay@....com>,
	<Ananth.narayan@....com>, Swapnil Sapkal <swapnil.sapkal@....com>
Subject: Re: [RFC PATCH 1/3] fs/pipe: Limit the slots in pipe_resize_ring()

Hello Oleg,

On 3/6/2025 5:58 PM, Oleg Nesterov wrote:
> On 03/06, K Prateek Nayak wrote:
>>
>> @@ -1272,6 +1272,10 @@ int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
>>   	struct pipe_buffer *bufs;
>>   	unsigned int head, tail, mask, n;
>>
>> +	/* nr_slots larger than limits of pipe->{head,tail} */
>> +	if (unlikely(nr_slots > BIT(BITS_PER_TYPE(pipe_index_t) - 1)))
> 
> Hmm, perhaps
> 
> 	if (nr_slots > (pipe_index_t)-1u)
> 
> is more clear?

Indeed it is. I didn't even know we could do that! Thank you for
pointing it out.

> 
> Oleg.
> 

-- 
Thanks and Regards,
Prateek