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pg_logicalinspect: Fix possible crash when passing a directory path.

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Previously, pg_logicalinspect functions were too trusting of their
input and blindly passed it to SnapBuildRestoreSnapshot(). If the
input pointed to a directory, the server could a PANIC error while
attempting to fsync_fname() with isdir=false on a directory.

This commit adds validation checks for input filenames and passes the
LSN extracted from the filename to SnapBuildRestoreSnapshot() instead
of the filename itself. It also adds regression tests for various
input patterns and permission checks.

Bug: #18828
Reported-by: Robins Tharakan <tharakan@gmail.com>
Co-authored-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Co-authored-by: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://postgr.es/m/18828-0f4701c635064211@postgresql.org
This commit is contained in:
Masahiko Sawada
2025-03-11 09:56:40 -07:00
parent a49927f04c
commit bd65cb3cd4
6 changed files with 183 additions and 18 deletions
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55
contrib/pg_logicalinspect/pg_logicalinspect.c
View File

@ -48,6 +48,45 @@ get_snapbuild_state_desc(SnapBuildState state)
return stateDesc;
}
/*
* Extract the LSN from the given serialized snapshot file name.
*/
static XLogRecPtr
parse_snapshot_filename(const char *filename)
{
uint32 hi;
uint32 lo;
XLogRecPtr lsn;
char tmpfname[MAXPGPATH];
/*
* Extract the values to build the LSN.
*
* Note: Including ".snap" doesn't mean that sscanf() also does the format
* check including the suffix. The subsequent check validates if the given
* filename has the expected suffix.
*/
if (sscanf(filename, "%X-%X.snap", &hi, &lo) != 2)
goto parse_error;
/*
* Bring back the extracted LSN to the snapshot file format and compare it
* to the given filename. This check strictly checks if the given filename
* follows the format of the snapshot filename.
*/
sprintf(tmpfname, "%X-%X.snap", hi, lo);
if (strcmp(tmpfname, filename) != 0)
goto parse_error;
lsn = ((uint64) hi) << 32 | lo;
return lsn;
parse_error:
ereport(ERROR,
errmsg("invalid snapshot file name \"%s\"", filename));
}
/*
* Retrieve the logical snapshot file metadata.
*/
@ -60,7 +99,7 @@ pg_get_logical_snapshot_meta(PG_FUNCTION_ARGS)
Datum values[PG_GET_LOGICAL_SNAPSHOT_META_COLS] = {0};
bool nulls[PG_GET_LOGICAL_SNAPSHOT_META_COLS] = {0};
TupleDesc tupdesc;
char path[MAXPGPATH];
XLogRecPtr lsn;
int i = 0;
text *filename_t = PG_GETARG_TEXT_PP(0);
@ -68,12 +107,10 @@ pg_get_logical_snapshot_meta(PG_FUNCTION_ARGS)
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
sprintf(path, "%s/%s",
PG_LOGICAL_SNAPSHOTS_DIR,
text_to_cstring(filename_t));
lsn = parse_snapshot_filename(text_to_cstring(filename_t));
/* Validate and restore the snapshot to 'ondisk' */
SnapBuildRestoreSnapshot(&ondisk, path, CurrentMemoryContext, false);
SnapBuildRestoreSnapshot(&ondisk, lsn, CurrentMemoryContext, false);
values[i++] = UInt32GetDatum(ondisk.magic);
values[i++] = Int64GetDatum((int64) ondisk.checksum);
@ -97,7 +134,7 @@ pg_get_logical_snapshot_info(PG_FUNCTION_ARGS)
Datum values[PG_GET_LOGICAL_SNAPSHOT_INFO_COLS] = {0};
bool nulls[PG_GET_LOGICAL_SNAPSHOT_INFO_COLS] = {0};
TupleDesc tupdesc;
char path[MAXPGPATH];
XLogRecPtr lsn;
int i = 0;
text *filename_t = PG_GETARG_TEXT_PP(0);
@ -105,12 +142,10 @@ pg_get_logical_snapshot_info(PG_FUNCTION_ARGS)
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
sprintf(path, "%s/%s",
PG_LOGICAL_SNAPSHOTS_DIR,
text_to_cstring(filename_t));
lsn = parse_snapshot_filename(text_to_cstring(filename_t));
/* Validate and restore the snapshot to 'ondisk' */
SnapBuildRestoreSnapshot(&ondisk, path, CurrentMemoryContext, false);
SnapBuildRestoreSnapshot(&ondisk, lsn, CurrentMemoryContext, false);
values[i++] = CStringGetTextDatum(get_snapbuild_state_desc(ondisk.builder.state));
values[i++] = TransactionIdGetDatum(ondisk.builder.xmin);