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Commit4372adf

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Fix possible NULL pointer dereference in GetNamedDSMSegment().
GetNamedDSMSegment() doesn't check whether dsm_attach() returnsNULL, which creates the possibility of a NULL pointer dereferencesoon after. To fix, emit an ERROR if dsm_attach() returns NULL.This shouldn't happen, but it would be nice to avoid a segfault ifit does. In passing, tidy up the surrounding code.Reported-by: Tom LaneReviewed-by: Michael Paquier, Bharath RupireddyDiscussion:https://postgr.es/m/3348869.1705854106%40sss.pgh.pa.us
1 parentcdd8634 commit4372adf

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+12
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‎src/backend/storage/ipc/dsm_registry.c

Lines changed: 12 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -177,19 +177,22 @@ GetNamedDSMSegment(const char *name, size_t size,
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(errmsg("requested DSM segment size does not match size of "
178178
"existing segment")));
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}
180-
elseif (!dsm_find_mapping(entry->handle))
180+
else
181181
{
182-
/* Attach to existing segment. */
183-
dsm_segment*seg=dsm_attach(entry->handle);
182+
dsm_segment*seg=dsm_find_mapping(entry->handle);
183+
184+
/* If the existing segment is not already attached, attach it now. */
185+
if (seg==NULL)
186+
{
187+
seg=dsm_attach(entry->handle);
188+
if (seg==NULL)
189+
elog(ERROR,"could not map dynamic shared memory segment");
190+
191+
dsm_pin_mapping(seg);
192+
}
184193

185-
dsm_pin_mapping(seg);
186194
ret=dsm_segment_address(seg);
187195
}
188-
else
189-
{
190-
/* Return address of an already-attached segment. */
191-
ret=dsm_segment_address(dsm_find_mapping(entry->handle));
192-
}
193196

194197
dshash_release_lock(dsm_registry_table,entry);
195198
MemoryContextSwitchTo(oldcontext);

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