linux-kernel - Re: [PATCH] RDMA/irdma: Fix a potential memory allocation issue in 'irdma_prm_add_pble

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Date:   Tue, 7 Dec 2021 13:51:10 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     mustafa.ismail@...el.com, shiraz.saleem@...el.com,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] RDMA/irdma: Fix a potential memory allocation issue in
 'irdma_prm_add_pble_mem()'

On Sun, Dec 05, 2021 at 09:17:24AM +0100, Christophe JAILLET wrote:
> 'pchunk->bitmapbuf' is a bitmap. Its size (in number of bits) is stored in
> 'pchunk->sizeofbitmap'.
> 
> When it is allocated, the size (in bytes) is computed by:
>    size_in_bits >> 3
> 
> There are 2 issues (numbers bellow assume that longs are 64 bits):
>    - there is no guarantee here that 'pchunk->bitmapmem.size' is modulo
>      BITS_PER_LONG but bitmaps are stored as longs
>      (sizeofbitmap=8 bits will only allocate 1 byte, instead of 8 (1 long))
> 
>    - the number of bytes is computed with a shift, not a round up, so we
>      may allocate less memory than needed
>      (sizeofbitmap=65 bits will only allocate 8 bytes (i.e. 1 long), when 2
>      longs are needed = 16 bytes)
> 
> Fix both issues by using 'bitmap_zalloc()' and remove the useless
> 'bitmapmem' from 'struct irdma_chunk'.
> 
> While at it, remove some useless NULL test before calling
> kfree/bitmap_free.
> 
> Fixes: 915cc7ac0f8e ("RDMA/irdma: Add miscellaneous utility definitions")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
>  drivers/infiniband/hw/irdma/pble.c  | 6 ++----
>  drivers/infiniband/hw/irdma/pble.h  | 1 -
>  drivers/infiniband/hw/irdma/utils.c | 9 ++-------
>  3 files changed, 4 insertions(+), 12 deletions(-)

Applied to for-rc, thanks

Jason