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