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crash after allocate string of negative size #33

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kcwu opened this issue Nov 6, 2016 · 2 comments

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commented Nov 6, 2016

input

00000000: 3c74 6162 6c65 3e3c 7461 626c 6520 6365  <table><table ce
00000010: 6c6c 7061 6464 696e 673d 3636 3036 3030  llpadding=660600
00000020: 3030 3030 3e30 3c74 643e 3c74 6578 7461  0000>0<td><texta
00000030: 7265 6120 726f 7773 3d34 3e3c 2f74 6162  rea rows=4></tab
00000040: 6c65 3c74 643e 3030                      le<td>00

crash location

Program received signal SIGSEGV, Segmentation fault.
0x000000000047967f in Strnew_size (n=-58) at Str.c:53
53  x->ptr[0] = '\0';
(gdb) p x->ptr
$1 = 0x0
(gdb) up
#1  0x000000000041e244 in flushline (h_env=0x7fff1b76ea60, obuf=0x7fff1b76ebf0, indent=0, force=0, width=-78) at file.c:2829
2829  o.line = Strnew_size(width + 20);
(gdb) bt
#0  0x000000000047967f in Strnew_size (n=-58) at Str.c:53
#1  0x000000000041e244 in flushline (h_env=0x7fff1b76ea60, obuf=0x7fff1b76ebf0, indent=0, force=0, width=-78) at file.c:2829
#2  0x000000000042c300 in HTMLlineproc0 (line=0x10ce1da "", h_env=0x7fff1b76ea60, internal=1) at file.c:6636
#3  0x0000000000442790 in do_refill (tbl=0x10ca2d0, row=0, col=1, maxlimit=-78) at table.c:798
#4  0x000000000044667b in renderTable (t=0x10ca2d0, max_width=23, h_env=0x7fff1b76f150) at table.c:1804
#5  0x0000000000445ea7 in renderCoTable (tbl=0x10c7e10, maxlimit=79) at table.c:1653
#6  0x00000000004465e8 in renderTable (t=0x10c7e10, max_width=78, h_env=0x7fff1b76f950) at table.c:1797
#7  0x000000000042b826 in HTMLlineproc0 (line=0x495779 "", h_env=0x7fff1b76f950, internal=1) at file.c:6444
#8  0x000000000042d3ec in completeHTMLstream (h_env=0x7fff1b76f950, obuf=0x7fff1b76fae0) at file.c:7013
#9  0x000000000042ddf7 in loadHTMLstream (f=0x7fff1b76ff70, newBuf=0x10c7770, src=0x0, internal=0) at file.c:7245
#10 0x000000000042c7db in loadHTMLBuffer (f=0x7fff1b76ff70, newBuf=0x10c7770) at file.c:6773
#11 0x0000000000416951 in loadSomething (f=0x7fff1b76ff70, loadproc=0x42c6c1 <loadHTMLBuffer>, defaultbuf=0x10c7770) at file.c:224
#12 0x000000000041c7c3 in loadGeneralFile (path=0x10c5160 "min/2", current=0x0, referer=0xffffffffffffffff <error: Cannot access memory at address 0xffffffffffffffff>, flag=0, request=0x0) at file.c:2241
#13 0x0000000000406fe2 in main (argc=5, argv=0x7fff1b770298, envp=0x7fff1b7702c8) at main.c:1020

With further debugging, I found the value -78 is coming from the result of LUsolve. At renderTable() line 1754 of table.c, the result of

1754             LUsolve(mat, pivot, t->vector, newwidth);
(gdb) p newwidth->ve[0]
$1 = -78.050371113549431

This is found by afl-fuzz.

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commented Nov 6, 2016

Anyway, 6606000000 is larger than INT_MAX. At file.c line 5022,

parsedtag_get_value(tag, ATTR_CELLPADDING, &y);

the result of y is -1983934592.
if (y < 0) y = 0; can fix this problem.

tats added a commit that referenced this issue Nov 7, 2016

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commented Nov 7, 2016

if (y < 0) y = 0; can fix this problem.

Check added. Thank you.

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