[Bug 613] New: diff -b with whitespace-only changes segfaults

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=613

              Host: i686-linux-gnu
            Target: i686-linux-gnu
             Build: i686-linux-gnu
           Summary: diff -b with whitespace-only changes segfaults
           Product: Busybox
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: critical
          Priority: P5
         Component: Other
        AssignedTo: vda.linux at googlemail.com
        ReportedBy: aldot at uclibc.org
                CC: busybox-cvs at busybox.net
   Estimated Hours: 0.0


$ echo " " > one
$ echo "  " > two
Starting program: /scratch/src/busybox/busybox_unstripped diff -b one two

Program received signal SIGSEGV, Segmentation fault.
0x08105cf1 in dump_unified_vec (f1=0x814e978, f2=0x814eae0)
    at editors/diff.c:775
775             lowa = MAX(1, cvp->a - opt_U_context);
(gdb) bt
#0  0x08105cf1 in dump_unified_vec (f1=0x814e978, f2=0x814eae0)
    at editors/diff.c:775
#1  0x08106355 in output (file1=0xbffff2ee "one", f1=0x814e978, 
    file2=0xbffff2f2 "two", f2=0x814eae0) at editors/diff.c:934
#2  0x0810671a in diffreg (file1=0xbffff2ee "one", file2=0xbffff2f2 "two", 
    flags=0) at editors/diff.c:1085
#3  0x08107099 in diff_main (argc=4, argv=0xbffff160) at editors/diff.c:1342
#4  0x0804f4c3 in run_applet_no_and_exit (applet_no=51, argv=0xbffff158)
    at libbb/appletlib.c:746
#5  0x0804f4f6 in run_applet_and_exit (name=0xbffff2e6 "diff", argv=0xbffff158)
    at libbb/appletlib.c:753
#6  0x0804f3ef in busybox_main (argv=0xbffff158) at libbb/appletlib.c:718
#7  0x0804f515 in run_applet_and_exit (name=0xbffff2d3 "busybox_unstripped", 
    argv=0xbffff154) at libbb/appletlib.c:755
#8  0x0804f5a4 in main (argc=5, argv=0xbffff154) at libbb/appletlib.c:808
(gdb) p cvp
$2 = (struct context_vec *) 0x0



$ valgrind ./busybox_unstripped diff -b one two
==5423== Memcheck, a memory error detector.
==5423== Copyright (C) 2002-2008, and GNU GPL'd, by Julian Seward et al.
==5423== Using LibVEX rev 1884, a library for dynamic binary translation.
==5423== Copyright (C) 2004-2008, and GNU GPL'd, by OpenWorks LLP.
==5423== Using valgrind-3.4.1-Debian, a dynamic binary instrumentation
framework.
==5423== Copyright (C) 2000-2008, and GNU GPL'd, by Julian Seward et al.
==5423== For more details, rerun with: -v
==5423== 
==5423== Invalid read of size 4
==5423==    at 0x8105CF1: dump_unified_vec (diff.c:775)
==5423==    by 0x804E6AC: ??? (start.S:119)
==5423==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
==5423== 
==5423== Process terminating with default action of signal 11 (SIGSEGV)
==5423==  Access not within mapped region at address 0x0
==5423==    at 0x8105CF1: dump_unified_vec (diff.c:775)
==5423==    by 0x804E6AC: ??? (start.S:119)


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