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From: "(GalaxyMaster)" <galaxy@openwall.com.au>
To: musl@lists.openwall.com
Cc: 2010267516@qq.com, Kaihang Zhang <kaihang.zhang@smartx.com>
Subject: Re: [musl] [PATCH] fix: Assign default value to mntent when linebuf is too small
Date: Tue, 12 Oct 2021 03:24:07 +0000	[thread overview]
Message-ID: <0100017c7287622f-cceed952-52dc-4c02-b1af-b3943a41203c-000000@email.amazonses.com> (raw)
In-Reply-To: <20211012023643.44509-1-kaihang.zhang@smartx.com>

Kaihang,

On Mon, Oct 11, 2021 at 10:36:43PM -0400, Kaihang Zhang wrote:
> Function getmntent_r in source misc/mntent.c will do what glibc users
> expect. The rest of the line will be discarded when can not be read
> into linebuf, and the fields of struct mntent will be assigned to empty
> string or zero when can not be found in linebuf, instead of setting
> errno to ERANGE and exiting.

Although this patch is on a similar topic as mine (changing the behaviour of
get*ent() funnctions), I think the change you are describing is considerable.

I would expect a function such as getmntent_r() which takes a user provided
buffer to fail and set ERANGE if the provided buffer is not enough to hold
the line.  This gives the developer an opportunity to recover, e.g. to
re-allocate a bigger buffer and try again.

In your proposal, I see two issues:

1. There is no feedback to the developer, so they have no idea whether the
   information they've got from the function was truncated or not (and what
   good does a truncated mnt line bring?);
2. There is no opportunity for the developer to realise a mistake they made
   by supplying too small buffer, hence there is no chance of recovering
   from it.

It is just my opinion and I would love to see other comments, since I have
not stumbled upon your use case yet and am not authoritative on this topic.

-- 
(GM)

  reply	other threads:[~2021-10-12 11:04 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-12  2:36 Kaihang Zhang
2021-10-12  3:24 ` (GalaxyMaster) [this message]
2021-10-12 12:59   ` Rich Felker
2021-10-15  7:19     ` Kaihang Zhang
2021-10-27 14:34     ` [musl] Changes to getmntent Alyssa Ross

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