Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit9c767ad

Browse files
committed
Improve pglz_decompress() so that it cannot clobber memory beyond the
available output buffer when presented with corrupt input. Some testingsuggests that this slows the decompression loop about 1%, which seems anacceptable price to pay for more robustness. (Curiously, the penaltyseems to be *less* on not-very-compressible data, which I didn't expectsince the overhead per output byte ought to be more in the literal-bytespath.)Patch from Zdenek Kotala. I fixed a corner case and did some renamingof variables to make the routine more readable.
1 parentad43447 commit9c767ad

File tree

1 file changed

+46
-31
lines changed

1 file changed

+46
-31
lines changed

‎src/backend/utils/adt/pg_lzcompress.c‎

Lines changed: 46 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -166,7 +166,7 @@
166166
*
167167
* Copyright (c) 1999-2008, PostgreSQL Global Development Group
168168
*
169-
* $PostgreSQL: pgsql/src/backend/utils/adt/pg_lzcompress.c,v 1.30 2008/03/07 23:20:21 tgl Exp $
169+
* $PostgreSQL: pgsql/src/backend/utils/adt/pg_lzcompress.c,v 1.31 2008/03/08 01:09:36 tgl Exp $
170170
* ----------
171171
*/
172172
#include"postgres.h"
@@ -641,26 +641,26 @@ pglz_compress(const char *source, int32 slen, PGLZ_Header *dest,
641641
void
642642
pglz_decompress(constPGLZ_Header*source,char*dest)
643643
{
644-
constunsignedchar*dp;
645-
constunsignedchar*dend;
646-
unsignedchar*bp;
647-
unsignedcharctrl;
648-
int32ctrlc;
649-
int32len;
650-
int32off;
651-
int32destsize;
652-
653-
dp= ((constunsignedchar*)source)+sizeof(PGLZ_Header);
654-
dend= ((constunsignedchar*)source)+VARSIZE(source);
655-
bp= (unsignedchar*)dest;
644+
constunsignedchar*sp;
645+
constunsignedchar*srcend;
646+
unsignedchar*dp;
647+
unsignedchar*destend;
656648

657-
while (dp<dend)
649+
sp= ((constunsignedchar*)source)+sizeof(PGLZ_Header);
650+
srcend= ((constunsignedchar*)source)+VARSIZE(source);
651+
dp= (unsignedchar*)dest;
652+
destend=dp+source->rawsize;
653+
654+
while (sp<srcend&&dp<destend)
658655
{
659656
/*
660-
* Read one control byte and process the next 8 items.
657+
* Read one control byte and process the next 8 items (or as many
658+
* as remain in the compressed input).
661659
*/
662-
ctrl=*dp++;
663-
for (ctrlc=0;ctrlc<8&&dp<dend;ctrlc++)
660+
unsignedcharctrl=*sp++;
661+
intctrlc;
662+
663+
for (ctrlc=0;ctrlc<8&&sp<srcend;ctrlc++)
664664
{
665665
if (ctrl&1)
666666
{
@@ -671,11 +671,27 @@ pglz_decompress(const PGLZ_Header *source, char *dest)
671671
* coded as 18, another extension tag byte tells how much
672672
* longer the match really was (0-255).
673673
*/
674-
len= (dp[0]&0x0f)+3;
675-
off= ((dp[0]&0xf0) <<4) |dp[1];
676-
dp+=2;
674+
int32len;
675+
int32off;
676+
677+
len= (sp[0]&0x0f)+3;
678+
off= ((sp[0]&0xf0) <<4) |sp[1];
679+
sp+=2;
677680
if (len==18)
678-
len+=*dp++;
681+
len+=*sp++;
682+
683+
/*
684+
* Check for output buffer overrun, to ensure we don't
685+
* clobber memory in case of corrupt input. Note: we must
686+
* advance dp here to ensure the error is detected below
687+
* the loop. We don't simply put the elog inside the loop
688+
* since that will probably interfere with optimization.
689+
*/
690+
if (dp+len>destend)
691+
{
692+
dp+=len;
693+
break;
694+
}
679695

680696
/*
681697
* Now we copy the bytes specified by the tag from OUTPUT to
@@ -685,8 +701,8 @@ pglz_decompress(const PGLZ_Header *source, char *dest)
685701
*/
686702
while (len--)
687703
{
688-
*bp=bp[-off];
689-
bp++;
704+
*dp=dp[-off];
705+
dp++;
690706
}
691707
}
692708
else
@@ -695,7 +711,10 @@ pglz_decompress(const PGLZ_Header *source, char *dest)
695711
* An unset control bit means LITERAL BYTE. So we just copy
696712
* one from INPUT to OUTPUT.
697713
*/
698-
*bp++=*dp++;
714+
if (dp >=destend)/* check for buffer overrun */
715+
break;/* do not clobber memory */
716+
717+
*dp++=*sp++;
699718
}
700719

701720
/*
@@ -706,14 +725,10 @@ pglz_decompress(const PGLZ_Header *source, char *dest)
706725
}
707726

708727
/*
709-
* Check we decompressed the right amount, else die. This is a FATAL
710-
* condition if we tromped on more memory than expected (we assume we have
711-
* not tromped on shared memory, though, so need not PANIC).
728+
* Check we decompressed the right amount.
712729
*/
713-
destsize= (char*)bp-dest;
714-
if (destsize!=source->rawsize)
715-
elog(destsize>source->rawsize ?FATAL :ERROR,
716-
"compressed data is corrupt");
730+
if (dp!=destend||sp!=srcend)
731+
elog(ERROR,"compressed data is corrupt");
717732

718733
/*
719734
* That's it.

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp