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Commitec03f2d

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Fix pg_restore's misdesigned code for detecting archive file format.
Despite the clear comments pointing out that the duplicative codesegments in ReadHead() and _discoverArchiveFormat() needed to bein sync, they were not: the latter did not bother to apply any ofthe sanity checks in the former. We'd missed noticing this partlybecause none of those checks would fail in scenarios we customarilytest, and partly because the oversight would be masked if bothsegments execute, which they would in cases other than needing toautodetect the format of a non-seekable stdin source. However,in a case meeting all these requirements --- for example, tryingto read a newer-than-supported archive format from non-seekablestdin --- pg_restore missed applying the version check and wouldlikely dump core or otherwise misbehave.The whole thing is silly anyway, because there seems little reasonto duplicate the logic beyond the one-line verification that thefile starts with "PGDMP". There seems to have been an undocumentedassumption that multiple major formats (major enough to requireseparate reader modules) would nonetheless share the first half-dozenfields of the custom-format header. This seems unlikely, so let'sfix it by just nuking the duplicate logic in _discoverArchiveFormat().Also get rid of the pointless attempt to seek back to the start ofthe file after successful autodetection. That wastes cycles andit means we have four behaviors to verify not two.Per bug #16951 from Sergey Koposov. This has been broken fordecades, so back-patch to all supported versions.Discussion:https://postgr.es/m/16951-a4dd68cf0de23048@postgresql.org
1 parent91e7c90 commitec03f2d

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3 files changed

+51
-110
lines changed

3 files changed

+51
-110
lines changed

‎src/bin/pg_dump/pg_backup_archiver.c

Lines changed: 39 additions & 98 deletions
Original file line numberDiff line numberDiff line change
@@ -2071,6 +2071,7 @@ _discoverArchiveFormat(ArchiveHandle *AH)
20712071
if (AH->lookahead)
20722072
free(AH->lookahead);
20732073

2074+
AH->readHeader=0;
20742075
AH->lookaheadSize=512;
20752076
AH->lookahead=pg_malloc0(512);
20762077
AH->lookaheadLen=0;
@@ -2142,62 +2143,9 @@ _discoverArchiveFormat(ArchiveHandle *AH)
21422143

21432144
if (strncmp(sig,"PGDMP",5)==0)
21442145
{
2145-
intbyteread;
2146-
charvmaj,
2147-
vmin,
2148-
vrev;
2149-
2150-
/*
2151-
* Finish reading (most of) a custom-format header.
2152-
*
2153-
* NB: this code must agree with ReadHead().
2154-
*/
2155-
if ((byteread=fgetc(fh))==EOF)
2156-
READ_ERROR_EXIT(fh);
2157-
2158-
vmaj=byteread;
2159-
2160-
if ((byteread=fgetc(fh))==EOF)
2161-
READ_ERROR_EXIT(fh);
2162-
2163-
vmin=byteread;
2164-
2165-
/* Save these too... */
2166-
AH->lookahead[AH->lookaheadLen++]=vmaj;
2167-
AH->lookahead[AH->lookaheadLen++]=vmin;
2168-
2169-
/* Check header version; varies from V1.0 */
2170-
if (vmaj>1|| (vmaj==1&&vmin>0))/* Version > 1.0 */
2171-
{
2172-
if ((byteread=fgetc(fh))==EOF)
2173-
READ_ERROR_EXIT(fh);
2174-
2175-
vrev=byteread;
2176-
AH->lookahead[AH->lookaheadLen++]=vrev;
2177-
}
2178-
else
2179-
vrev=0;
2180-
2181-
AH->version=MAKE_ARCHIVE_VERSION(vmaj,vmin,vrev);
2182-
2183-
if ((AH->intSize=fgetc(fh))==EOF)
2184-
READ_ERROR_EXIT(fh);
2185-
AH->lookahead[AH->lookaheadLen++]=AH->intSize;
2186-
2187-
if (AH->version >=K_VERS_1_7)
2188-
{
2189-
if ((AH->offSize=fgetc(fh))==EOF)
2190-
READ_ERROR_EXIT(fh);
2191-
AH->lookahead[AH->lookaheadLen++]=AH->offSize;
2192-
}
2193-
else
2194-
AH->offSize=AH->intSize;
2195-
2196-
if ((byteread=fgetc(fh))==EOF)
2197-
READ_ERROR_EXIT(fh);
2198-
2199-
AH->format=byteread;
2200-
AH->lookahead[AH->lookaheadLen++]=AH->format;
2146+
/* It's custom format, stop here */
2147+
AH->format=archCustom;
2148+
AH->readHeader=1;
22012149
}
22022150
else
22032151
{
@@ -2234,22 +2182,15 @@ _discoverArchiveFormat(ArchiveHandle *AH)
22342182
AH->format=archTar;
22352183
}
22362184

2237-
/* If we can't seek, then mark the header as read */
2238-
if (fseeko(fh,0,SEEK_SET)!=0)
2239-
{
2240-
/*
2241-
* NOTE: Formats that use the lookahead buffer can unset this in their
2242-
* Init routine.
2243-
*/
2244-
AH->readHeader=1;
2245-
}
2246-
else
2247-
AH->lookaheadLen=0;/* Don't bother since we've reset the file */
2248-
2249-
/* Close the file */
2185+
/* Close the file if we opened it */
22502186
if (wantClose)
2187+
{
22512188
if (fclose(fh)!=0)
22522189
fatal("could not close input file: %m");
2190+
/* Forget lookahead, since we'll re-read header after re-opening */
2191+
AH->readHeader=0;
2192+
AH->lookaheadLen=0;
2193+
}
22532194

22542195
returnAH->format;
22552196
}
@@ -3790,7 +3731,9 @@ WriteHead(ArchiveHandle *AH)
37903731
void
37913732
ReadHead(ArchiveHandle*AH)
37923733
{
3793-
chartmpMag[7];
3734+
charvmaj,
3735+
vmin,
3736+
vrev;
37943737
intfmt;
37953738
structtmcrtm;
37963739

@@ -3802,48 +3745,46 @@ ReadHead(ArchiveHandle *AH)
38023745
*/
38033746
if (!AH->readHeader)
38043747
{
3805-
charvmaj,
3806-
vmin,
3807-
vrev;
3748+
chartmpMag[7];
38083749

38093750
AH->ReadBufPtr(AH,tmpMag,5);
38103751

38113752
if (strncmp(tmpMag,"PGDMP",5)!=0)
38123753
fatal("did not find magic string in file header");
3754+
}
38133755

3814-
vmaj=AH->ReadBytePtr(AH);
3815-
vmin=AH->ReadBytePtr(AH);
3756+
vmaj=AH->ReadBytePtr(AH);
3757+
vmin=AH->ReadBytePtr(AH);
38163758

3817-
if (vmaj>1|| (vmaj==1&&vmin>0))/* Version > 1.0 */
3818-
vrev=AH->ReadBytePtr(AH);
3819-
else
3820-
vrev=0;
3759+
if (vmaj>1|| (vmaj==1&&vmin>0))/* Version > 1.0 */
3760+
vrev=AH->ReadBytePtr(AH);
3761+
else
3762+
vrev=0;
38213763

3822-
AH->version=MAKE_ARCHIVE_VERSION(vmaj,vmin,vrev);
3764+
AH->version=MAKE_ARCHIVE_VERSION(vmaj,vmin,vrev);
38233765

3824-
if (AH->version<K_VERS_1_0||AH->version>K_VERS_MAX)
3825-
fatal("unsupported version (%d.%d) in file header",
3826-
vmaj,vmin);
3766+
if (AH->version<K_VERS_1_0||AH->version>K_VERS_MAX)
3767+
fatal("unsupported version (%d.%d) in file header",
3768+
vmaj,vmin);
38273769

3828-
AH->intSize=AH->ReadBytePtr(AH);
3829-
if (AH->intSize>32)
3830-
fatal("sanity check on integer size (%lu) failed",
3831-
(unsigned long)AH->intSize);
3770+
AH->intSize=AH->ReadBytePtr(AH);
3771+
if (AH->intSize>32)
3772+
fatal("sanity check on integer size (%lu) failed",
3773+
(unsigned long)AH->intSize);
38323774

3833-
if (AH->intSize>sizeof(int))
3834-
pg_log_warning("archive was made on a machine with larger integers, some operations might fail");
3775+
if (AH->intSize>sizeof(int))
3776+
pg_log_warning("archive was made on a machine with larger integers, some operations might fail");
38353777

3836-
if (AH->version >=K_VERS_1_7)
3837-
AH->offSize=AH->ReadBytePtr(AH);
3838-
else
3839-
AH->offSize=AH->intSize;
3778+
if (AH->version >=K_VERS_1_7)
3779+
AH->offSize=AH->ReadBytePtr(AH);
3780+
else
3781+
AH->offSize=AH->intSize;
38403782

3841-
fmt=AH->ReadBytePtr(AH);
3783+
fmt=AH->ReadBytePtr(AH);
38423784

3843-
if (AH->format!=fmt)
3844-
fatal("expected format (%d) differs from format found in file (%d)",
3845-
AH->format,fmt);
3846-
}
3785+
if (AH->format!=fmt)
3786+
fatal("expected format (%d) differs from format found in file (%d)",
3787+
AH->format,fmt);
38473788

38483789
if (AH->version >=K_VERS_1_2)
38493790
{

‎src/bin/pg_dump/pg_backup_archiver.h

Lines changed: 12 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -253,15 +253,21 @@ struct _archiveHandle
253253
time_tcreateDate;/* Date archive created */
254254

255255
/*
256-
* Fields used when discovering header. A format can always get the
257-
* previous read bytes from here...
256+
* Fields used when discovering archive format. For tar format, we load
257+
* the first block into the lookahead buffer, and verify that it looks
258+
* like a tar header. The tar module must then consume bytes from the
259+
* lookahead buffer before reading any more from the file. For custom
260+
* format, we load only the "PGDMP" marker into the buffer, and then set
261+
* readHeader after confirming it matches. The buffer is vestigial in
262+
* this case, as the subsequent code just checks readHeader and doesn't
263+
* examine the buffer.
258264
*/
259-
intreadHeader;/*Used iffile header has beenreadalready */
265+
intreadHeader;/*Set ifwe alreadyread"PGDMP" marker */
260266
char*lookahead;/* Buffer used when reading header to discover
261267
* format */
262-
size_tlookaheadSize;/*Size of allocated buffer */
263-
size_tlookaheadLen;/* Length of data in lookahead */
264-
pgoff_tlookaheadPos;/* Current read position in lookahead buffer */
268+
size_tlookaheadSize;/*Allocated size of buffer */
269+
size_tlookaheadLen;/* Length ofvaliddata in lookahead */
270+
size_tlookaheadPos;/* Current read position in lookahead buffer */
265271

266272
ArchiveEntryPtrTypeArchiveEntryPtr;/* Called for each metadata object */
267273
StartDataPtrTypeStartDataPtr;/* Called when table data is about to be

‎src/bin/pg_dump/pg_backup_tar.c

Lines changed: 0 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -228,12 +228,6 @@ InitArchiveFmt_Tar(ArchiveHandle *AH)
228228

229229
ctx->hasSeek=checkSeek(ctx->tarFH);
230230

231-
/*
232-
* Forcibly unmark the header as read since we use the lookahead
233-
* buffer
234-
*/
235-
AH->readHeader=0;
236-
237231
ctx->FH= (void*)tarOpen(AH,"toc.dat",'r');
238232
ReadHead(AH);
239233
ReadToc(AH);

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