[PATCH] mke2fs: Escape double quotes when parsing mke2fs.conf

[PATCH] mke2fs: Escape double quotes when parsing mke2fs.conf

[Lukas Czerner]

Currently, when constructing the <default> configuration pseudo-file using
the profile-to-c.awk script we will just pass the double quotes as they
appear in the mke2fs.conf.

This is problematic, because the resulting default_profile.c will either
fail to compile because of syntax error, or leave the resulting
configuration invalid.

It can be reproduced by adding the following line somewhere into
mke2fs.conf configuration and forcing mke2fs to use the <default>
configuration by specifying nonexistent mke2fs.conf

MKE2FS_CONFIG="nonexistent" ./misc/mke2fs -T ext4 /dev/device

default_mntopts = "acl,user_xattr"
^ this will fail to compile

default_mntopts = ""
^ this will result in invalid config file

Syntax error in mke2fs config file (<default>, line #4)
       Unknown code prof 17

Fix it by escaping the double quotes with a backslash in
profile-to-c.awk script.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
 misc/profile-to-c.awk | 1 +
 1 file changed, 1 insertion(+)

diff --git a/misc/profile-to-c.awk b/misc/profile-to-c.awk
index f964efd6..814f7236 100644
--- a/misc/profile-to-c.awk
+++ b/misc/profile-to-c.awk
@@ -4,6 +4,7 @@ BEGIN {
 }
 
 {
+  gsub("\"","\\\"",$0);
   printf("  \"%s\\n\"\n", $0);
 }
 
-- 
2.26.2

Re: [PATCH] mke2fs: Escape double quotes when parsing mke2fs.conf

[Andreas Dilger]

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On Nov 2, 2020, at 7:26 AM, Lukas Czerner <lczerner@redhat.com> wrote:
> 
> Currently, when constructing the <default> configuration pseudo-file using
> the profile-to-c.awk script we will just pass the double quotes as they
> appear in the mke2fs.conf.
> 
> This is problematic, because the resulting default_profile.c will either
> fail to compile because of syntax error, or leave the resulting
> configuration invalid.
> 
> It can be reproduced by adding the following line somewhere into
> mke2fs.conf configuration and forcing mke2fs to use the <default>
> configuration by specifying nonexistent mke2fs.conf
> 
> MKE2FS_CONFIG="nonexistent" ./misc/mke2fs -T ext4 /dev/device
> 
> default_mntopts = "acl,user_xattr"
> ^ this will fail to compile
> 
> default_mntopts = ""
> ^ this will result in invalid config file
> 
> Syntax error in mke2fs config file (<default>, line #4)
>       Unknown code prof 17
> 
> Fix it by escaping the double quotes with a backslash in
> profile-to-c.awk script.

What about using single quotes for this?  That avoids the need to escape
the double quotes, and avoids significant issues (IMHO) when the number
of escapes grows over time as they are swallowed by various levels of
processing.

Cheers, Andreas

> 
> Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> ---
> misc/profile-to-c.awk | 1 +
> 1 file changed, 1 insertion(+)
> 
> diff --git a/misc/profile-to-c.awk b/misc/profile-to-c.awk
> index f964efd6..814f7236 100644
> --- a/misc/profile-to-c.awk
> +++ b/misc/profile-to-c.awk
> @@ -4,6 +4,7 @@ BEGIN {
> }
> 
> {
> +  gsub("\"","\\\"",$0);
>   printf("  \"%s\\n\"\n", $0);
> }
> 
> --
> 2.26.2
> 


Cheers, Andreas






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Re: [PATCH] mke2fs: Escape double quotes when parsing mke2fs.conf

[Lukas Czerner]

On Mon, Nov 02, 2020 at 02:37:38PM -0700, Andreas Dilger wrote:
> On Nov 2, 2020, at 7:26 AM, Lukas Czerner <lczerner@redhat.com> wrote:
> > 
> > Currently, when constructing the <default> configuration pseudo-file using
> > the profile-to-c.awk script we will just pass the double quotes as they
> > appear in the mke2fs.conf.
> > 
> > This is problematic, because the resulting default_profile.c will either
> > fail to compile because of syntax error, or leave the resulting
> > configuration invalid.
> > 
> > It can be reproduced by adding the following line somewhere into
> > mke2fs.conf configuration and forcing mke2fs to use the <default>
> > configuration by specifying nonexistent mke2fs.conf
> > 
> > MKE2FS_CONFIG="nonexistent" ./misc/mke2fs -T ext4 /dev/device
> > 
> > default_mntopts = "acl,user_xattr"
> > ^ this will fail to compile
> > 
> > default_mntopts = ""
> > ^ this will result in invalid config file
> > 
> > Syntax error in mke2fs config file (<default>, line #4)
> >       Unknown code prof 17
> > 
> > Fix it by escaping the double quotes with a backslash in
> > profile-to-c.awk script.
> 
> What about using single quotes for this?  That avoids the need to escape
> the double quotes, and avoids significant issues (IMHO) when the number
> of escapes grows over time as they are swallowed by various levels of
> processing.

Hi Andreas,

I am not sure I understand what issues you have in mind. The way I see
it, the profile-to-c.awk is used just during compile time to generate a
mke2fs_default_profile string and that's consumed by mke2fs in the case
no external config file can be found. There is only one level, or am I
missing something ?

Regardless it is possible to use a single quote by changing the code in
parse_line(). However I don't think we can just stop supporting double
quotes since that would technically change the mke2fs.conf format so it
would not solve the problem.

Thanks
-Lukas

> 
> Cheers, Andreas
> 
> > 
> > Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> > ---
> > misc/profile-to-c.awk | 1 +
> > 1 file changed, 1 insertion(+)
> > 
> > diff --git a/misc/profile-to-c.awk b/misc/profile-to-c.awk
> > index f964efd6..814f7236 100644
> > --- a/misc/profile-to-c.awk
> > +++ b/misc/profile-to-c.awk
> > @@ -4,6 +4,7 @@ BEGIN {
> > }
> > 
> > {
> > +  gsub("\"","\\\"",$0);
> >   printf("  \"%s\\n\"\n", $0);
> > }
> > 
> > --
> > 2.26.2
> > 
> 
> 
> Cheers, Andreas
> 
> 
> 
> 
> 

Re: [PATCH] mke2fs: Escape double quotes when parsing mke2fs.conf

[Theodore Ts'o]

On Mon, Nov 02, 2020 at 03:26:31PM +0100, Lukas Czerner wrote:
> Currently, when constructing the <default> configuration pseudo-file using
> the profile-to-c.awk script we will just pass the double quotes as they
> appear in the mke2fs.conf.
> 
> This is problematic, because the resulting default_profile.c will either
> fail to compile because of syntax error, or leave the resulting
> configuration invalid.

Applied, thanks.

					- Ted