linux-kernel - Re: [PATCH] mm/mmap: Fix error return in do_vmi_align

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Message-ID: <2023062852-cyclic-presuming-6490@gregkh>
Date:   Wed, 28 Jun 2023 12:52:04 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     David Woodhouse <dwmw2@...radead.org>
Cc:     "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/mmap: Fix error return in do_vmi_align_munmap()

On Wed, Jun 28, 2023 at 11:42:45AM +0100, David Woodhouse wrote:
> From: David Woodhouse <dwmw@...zon.co.uk>
> 
> If mas_store_gfp() in the gather loop failed, the 'error' variable that
> ultimately gets returned was not being set. In many cases, its original
> value of -ENOMEM was still in place, and that was fine. But if VMAs had
> been split at the start or end of the range, then 'error' could be zero.
> 
> Change to the 'error = foo(); if (error) goto …' idiom to fix the bug.
> 
> Also clean up a later case which avoided the same bug by *explicitly*
> setting error = -ENOMEM right before calling the function that might
> return -ENOMEM.
> 
> In a final cosmetic change, move the 'Point of no return' comment to
> *after* the goto. That's been in the wrong place since the preallocation
> was removed, and this new error path was added.
> 
> Fixes: 606c812eb1d5 ("mm/mmap: Fix error path in do_vmi_align_munmap()")
> Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
> ---
>  mm/mmap.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>