[RFC PATCH 1/1] patch: fix seg fault caused by malformed patch
Jim Keniston
jkenisto at linux.vnet.ibm.com
Thu Mar 5 23:58:45 UTC 2015
The busybox FAQ says it's time to post a polite reminder about my
suggested patch. See my original mail below.
Here's a sample patch that triggers the seg fault:
=== cut here ===
-- dwarves.orig 2015-02-25 01:45:27.753000000 +0000
+++ dwarves 2015-02-25 01:46:08.199000000 +0000
@@ -1,7 +1,7 @@
Bashful
Doc
Dopey
-Grouchy
+Grumpy
Happy
Sleepy
Sneezy
=== cut here ===
BTW, if you don't mind spending ~20 bytes of rodata for potentially
clearer error messages, you could do
+ if (!oldname)
+ oldname = xstrdup("MISSING_FILENAME");
+ else if (!newname)
+ newname = xstrdup("MISSING_FILENAME");
instead.
Jim Keniston
On Thu, 2015-02-26 at 15:10 -0800, Jim Keniston wrote:
> busybox's patch command dies with a SIGSEGV if the "---" line that heralds
> a new file to patch is missing. GNU patch silently does what's apparently
> wanted, based on the "+++" line.
>
> Signed-off-by: Jim Keniston <jkenisto at linux.vnet.ibm.com>
>
> diff -up ./editors/patch.c.orig ./editors/patch.c
> --- ./editors/patch.c.orig 2015-02-25 18:28:29.231096889 -0600
> +++ ./editors/patch.c 2015-02-26 16:21:23.560131205 -0600
> @@ -345,6 +345,8 @@ done:
> // state 1: Found +++ file indicator, look for @@
> // state 2: In hunk: counting initial context lines
> // state 3: In hunk: getting body
> +// Like GNU patch, we don't require a --- line before the +++, and
> +// also allow the --- after the +++ line.
>
> int patch_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
> int patch_main(int argc UNUSED_PARAM, char **argv)
> @@ -462,6 +464,14 @@ int patch_main(int argc UNUSED_PARAM, ch
> TT.context = 0;
> state = 2;
>
> + // If the --- line is missing or malformed, either oldname
> + // or (for -R) newname could be NULL -- but not both. Like
> + // GNU patch, proceed based on the +++ line, and avoid SEGVs.
> + if (!oldname)
> + oldname = xstrdup(newname);
> + else if (!newname)
> + newname = xstrdup(oldname);
> +
> // If this is the first hunk, open the file.
> if (TT.filein == -1) {
> int oldsum, newsum, empty = 0;
>
>
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