[nft PATCH] scanner: fix reading of really long line

[nft PATCH] scanner: fix reading of really long line

[Eric Leblond]

Current code is causing a failure in adding a set containing
a really long list of elements. The failure occurs as soon as
the line is longer than flex read buffer.

When a line is longer than scanner buffer size, the code in YY_INPUT
forces a rewind to the beginning of the string because it does not
find a end of line. The result is that the string is never parsed.

This patch updates the code by rewinding till we found a space.

Signed-off-by: Eric Leblond <eric@regit.org>
---
 src/scanner.l | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/scanner.l b/src/scanner.l
index f0ed8d4..2fafa71 100644
--- a/src/scanner.l
+++ b/src/scanner.l
@@ -47,7 +47,8 @@
 		clearerr(yyin);							\
 	}									\
 	if (result > 1) {							\
-		while (result > 1 && buf[result - 1] != '\n')			\
+		while (result > 1 && 						\
+		       (buf[result - 1] != '\n' &&  buf[result - 1] != ' '))	\
 			result--, n++;						\
 		result--, n++;							\
 		fseek(yyin, -n, SEEK_CUR);					\
-- 
2.1.3

Re: [nft PATCH] scanner: fix reading of really long line

[Pablo Neira Ayuso]

On Sat, Nov 29, 2014 at 05:24:38PM +0100, Eric Leblond wrote:
> Current code is causing a failure in adding a set containing
> a really long list of elements. The failure occurs as soon as
> the line is longer than flex read buffer.
> 
> When a line is longer than scanner buffer size, the code in YY_INPUT
> forces a rewind to the beginning of the string because it does not
> find a end of line. The result is that the string is never parsed.
> 
> This patch updates the code by rewinding till we found a space.

But the part that didn't fit in will be ignore, right? So the user
will lose some elements in the set?

If so, I think it's better to spot an error via YY_FATAL_ERROR to
indicate that the line is too long to the user.

Re: [nft PATCH] scanner: fix reading of really long line

[Eric Leblond]

Hello,
Le 1 déc. 2014 12:55, Pablo Neira Ayuso <pablo@netfilter.org> a écrit :
>
> On Sat, Nov 29, 2014 at 05:24:38PM +0100, Eric Leblond wrote: 
> > Current code is causing a failure in adding a set containing 
> > a really long list of elements. The failure occurs as soon as 
> > the line is longer than flex read buffer. 
> > 
> > When a line is longer than scanner buffer size, the code in YY_INPUT 
> > forces a rewind to the beginning of the string because it does not 
> > find a end of line. The result is that the string is never parsed. 
> > 
> > This patch updates the code by rewinding till we found a space. 
>
> But the part that didn't fit in will be ignore, right? So the user 
> will lose some elements in the set? 

This is not the case as there is a fseek below to rewind at the correct position. So next read get the data from the correct point.

BR,

> If so, I think it's better to spot an error via YY_FATAL_ERROR to 
> indicate that the line is too long to the user. 

Re: [nft PATCH] scanner: fix reading of really long line

[Pablo Neira Ayuso]

On Mon, Dec 01, 2014 at 02:46:04PM +0100, Eric Leblond wrote:
> Hello,
> Le 1 déc. 2014 12:55, Pablo Neira Ayuso <pablo@netfilter.org> a écrit :
> >
> > On Sat, Nov 29, 2014 at 05:24:38PM +0100, Eric Leblond wrote: 
> > > Current code is causing a failure in adding a set containing 
> > > a really long list of elements. The failure occurs as soon as 
> > > the line is longer than flex read buffer. 
> > > 
> > > When a line is longer than scanner buffer size, the code in YY_INPUT 
> > > forces a rewind to the beginning of the string because it does not 
> > > find a end of line. The result is that the string is never parsed. 
> > > 
> > > This patch updates the code by rewinding till we found a space. 
> >
> > But the part that didn't fit in will be ignore, right? So the user 
> > will lose some elements in the set? 
> 
> This is not the case as there is a fseek below to rewind at the correct position. So next read get the data from the correct point.

OK. Applied, thanks.
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