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Message-ID: <e00fb341-093a-4c39-2f4b-d3a938e7e5ad@mail.ustc.edu.cn>
Date: Mon, 11 Apr 2022 00:39:33 +0800
From: Keyu Tao <taoky@...l.ustc.edu.cn>
To: musl@...ts.openwall.com
Cc: alex_y_xu@...oo.ca
Subject: Re: getmntent() fails to parse when source is empty string
Thank you for your reply.
I once believed that glibc can handle the leading whitespace as `mount`
in my host is working correctly. I rechecked just now and found that the
`mount` in Alpine container is provided by busybox, which uses
`getmntent_r()` to parse /proc/mounts (in mount_main()). However, the
`mount` in my host is provided by util-linux package rather than
busybox, and it does not use `getmntent()`. I used `ltrace` to see all
library function calls, and the busybox mount implementation in glibc
also provides incorrect result like this:
getmntent_r(0x555adeefa2c0, { "/tmp/test1", "tmpfs",
"rw,nosuid,nodev,relatime,inode64"..., "0", 0, 0 }, " /tmp/test1", 1016)
= { "/tmp/test1", "tmpfs", "rw,nosuid,nodev,relatime,inode64"..., "0",
0, 0 }
getmntent_r(0x555adeefa2c0, { "none", "/tmp/test2", "tmpfs",
"rw,nosuid,nodev,relatime,inode64"..., 0, 0 }, "none", 1016) = { "none",
"/tmp/test2", "tmpfs", "rw,nosuid,nodev,relatime,inode64"..., 0, 0 }
It looks like not a bug of musl now :-).
在 2022/4/11 00:00, Alex Xu (Hello71) 写道:
> It's worth noting that octal escape sequences are also not supported.
> This has been reported previously, e.g. at:
>
> https://inbox.vuxu.org/musl/HE1P192MB0010D60AAC4BA0F08F1A5644FB5E0@HE1P192MB0010.EURP192.PROD.OUTLOOK.COM/
>
> https://inbox.vuxu.org/musl/87o85j8sru.fsf@atufi.org/
>
> I think the empty source is basically impossible to support with
> getmntent though. Both the glibc and musl implementations ignore leading
> whitespace, probably because getmntent is more commonly used with fstab,
> where users may have unintentional leading whitespace. If empty sources
> are an issue for your program, I would suggest using your own getmntent
> implementation.
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