bug#28120: [PATCH] ptx: fix a possible crash caused by integer overflow

[Kamil Dudka]

The crash might not be reproducible in all environments but I was able
to observe invalid reads by valgrind while running ptx on the reproducer
for <https://bugzilla.redhat.com/1482445>:

% curl -s 'https://bugzilla.redhat.com/attachment.cgi?id=1314625' | gzip -cd | 
valgrind ptx > /dev/null
==4288== Memcheck, a memory error detector
==4288== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==4288== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright info
==4288== Command: ptx
==4288==
==4288== Invalid read of size 1
==4288==    at 0x402FA9: define_all_fields (ptx.c:1434)
==4288==    by 0x402FA9: generate_all_output (ptx.c:1780)
==4288==    by 0x402FA9: main (ptx.c:2155)
==4288==  Address 0x5328a6f is 2,287 bytes inside a block of size 16,352 free'd
==4288==    at 0x4C2FC47: realloc (vg_replace_malloc.c:785)
==4288==    by 0x408B65: xrealloc (xmalloc.c:61)
==4288==    by 0x402857: find_occurs_in_text (ptx.c:955)
==4288==    by 0x402857: main (ptx.c:2141)
==4288==  Block was alloc'd at
==4288==    at 0x4C2FC47: realloc (vg_replace_malloc.c:785)
==4288==    by 0x408B65: xrealloc (xmalloc.c:61)
==4288==    by 0x402857: find_occurs_in_text (ptx.c:955)
==4288==    by 0x402857: main (ptx.c:2141)
==4288==
==4288== Invalid read of size 1
==4288==    at 0x4031AB: define_all_fields (ptx.c:1501)
==4288==    by 0x4031AB: generate_all_output (ptx.c:1780)
==4288==    by 0x4031AB: main (ptx.c:2155)
==4288==  Address 0x5328a6f is 2,287 bytes inside a block of size 16,352 free'd
==4288==    at 0x4C2FC47: realloc (vg_replace_malloc.c:785)
==4288==    by 0x408B65: xrealloc (xmalloc.c:61)
==4288==    by 0x402857: find_occurs_in_text (ptx.c:955)
==4288==    by 0x402857: main (ptx.c:2141)
==4288==  Block was alloc'd at
==4288==    at 0x4C2FC47: realloc (vg_replace_malloc.c:785)
==4288==    by 0x408B65: xrealloc (xmalloc.c:61)
==4288==    by 0x402857: find_occurs_in_text (ptx.c:955)
==4288==    by 0x402857: main (ptx.c:2141)
==4288==
==4288==
==4288== HEAP SUMMARY:
==4288==     in use at exit: 2,340,851 bytes in 96 blocks
==4288==   total heap usage: 200 allocs, 104 frees, 6,478,142 bytes allocated
==4288==
==4288== LEAK SUMMARY:
==4288==    definitely lost: 0 bytes in 0 blocks
==4288==    indirectly lost: 0 bytes in 0 blocks
==4288==      possibly lost: 0 bytes in 0 blocks
==4288==    still reachable: 2,340,851 bytes in 96 blocks
==4288==         suppressed: 0 bytes in 0 blocks
==4288== Rerun with --leak-check=full to see details of leaked memory
==4288==
==4288== For counts of detected and suppressed errors, rerun with: -v
==4288== ERROR SUMMARY: 915 errors from 2 contexts (suppressed: 0 from 0)
---
 src/ptx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ptx.c b/src/ptx.c
index c0c9733..f4ed7d4 100644
--- a/src/ptx.c
+++ b/src/ptx.c
@@ -224,7 +224,7 @@ static BLOCK *text_buffers; /* files to study */
    start of the reference field, it is of type (DELTA) and usually
    negative.  */
 
-typedef short int DELTA;       /* to hold displacement within one context */
+typedef int DELTA;             /* to hold displacement within one context */
 
 typedef struct
   {
-- 
2.9.5