fix two crashes in mandocdb

fix two crashes in mandocdb

[Ingo Schwarze]

Hi,

here are two easy, but important bugfixes for mandocdb(8).

Chunk 1 is required such that mandocdb doesn't die on extremely
long files.  In my /usr/share/man tree, i have a few very large
files - not real manuals, but they get in the way.

The man parser produces several tens of thousands of text nodes
from these files.  When mandocdb.c attempts to parse them, it
abuses recursion to walk a linear list, resulting in O(N)
stack size requirements.  Stacks with several tens of thousands
of frames don't work well, the program consistently segfaulted;
overflowing thew stack, i guess.

With the for loop, time requirements are still O(N), but at
least we get constant stack size.  I guess we should scour
the tree for similar bugs.  This might as well crash massively
oversized man(7) manuals during normal formatting.


Chunk 2 is required to avoid running out of file descriptors
when walking large directory trees.  Otherwise, mandocdb keeps
crashing on me because it hits the system resource limit on
open file descriptors.


Using this, i can now run

  # mandocdb /usr/share/man

on my main development machine.

OK?
  Ingo


--- mandocdb.c.orig
+++ mandocdb.c
@@ -1142,10 +1142,9 @@ pman_node(MAN_ARGS)
 		}
 	}
 
-	if (pman_node(hash, buf, dbuf, n->child))
-		return(1);
-	if (pman_node(hash, buf, dbuf, n->next))
-		return(1);
+	for (n = n->child; n; n = n->next)
+		if (pman_node(hash, buf, dbuf, n))
+			return(1);
 
 	return(0);
 }
@@ -1250,6 +1249,7 @@ ofile_dirbuild(const char *dir, int verb, struct of **of)
 		}
 	}
 
+	closedir(d);
 	return(1);
 }
 
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Re: fix two crashes in mandocdb

[Kristaps Dzonsons]

On 13/11/2011 01:09, Ingo Schwarze wrote:
> Hi,
>
> here are two easy, but important bugfixes for mandocdb(8).
>
> Chunk 1 is required such that mandocdb doesn't die on extremely
> long files.  In my /usr/share/man tree, i have a few very large
> files - not real manuals, but they get in the way.
>
> The man parser produces several tens of thousands of text nodes
> from these files.  When mandocdb.c attempts to parse them, it
> abuses recursion to walk a linear list, resulting in O(N)
> stack size requirements.  Stacks with several tens of thousands
> of frames don't work well, the program consistently segfaulted;
> overflowing thew stack, i guess.
>
> With the for loop, time requirements are still O(N), but at
> least we get constant stack size.  I guess we should scour
> the tree for similar bugs.  This might as well crash massively
> oversized man(7) manuals during normal formatting.
>
>
> Chunk 2 is required to avoid running out of file descriptors
> when walking large directory trees.  Otherwise, mandocdb keeps
> crashing on me because it hits the system resource limit on
> open file descriptors.
>
>
> Using this, i can now run
>
>    # mandocdb /usr/share/man
>
> on my main development machine.
>
> OK?

Ingo, great find!  Please check this in.

Thanks again,

Kristaps

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