Hi Junwang, On Mon, Jul 8, 2024 at 7:08 PM Junwang Zhao <zhjw...@gmail.com> wrote: > On Mon, Jul 8, 2024 at 3:22 PM Nitin Jadhav > <nitinjadhavpostg...@gmail.com> wrote: > > > > In [1], Andres reported a -Wuse-after-free bug in the > > ATExecAttachPartition() function. I've created a patch to address it > > with pointers from Amit offlist. > > > > The issue was that the partBoundConstraint variable was utilized after > > the list_concat() function. This could potentially lead to accessing > > the partBoundConstraint variable after its memory has been freed. > > > > The issue was resolved by using the return value of the list_concat() > > function, instead of using the list1 argument of list_concat(). I > > copied the partBoundConstraint variable to a new variable named > > partConstraint and used it for the previous references before invoking > > get_proposed_default_constraint(). I confirmed that the > > eval_const_expressions(), make_ands_explicit(), > > map_partition_varattnos(), QueuePartitionConstraintValidation() > > functions do not modify the memory location pointed to by the > > partBoundConstraint variable. Therefore, it is safe to use it for the > > next reference in get_proposed_default_constraint() > > > > Attaching the patch. Please review and share the comments if any. > > Thanks to Andres for spotting the bug and some off-list advice on how > > to reproduce it. > > The patch LGTM. > > Curious how to reproduce the bug ;)
Download and apply (`git am`) Andres' patch to "add allocator attributes" here (note it's not merged into the tree yet!): https://github.com/anarazel/postgres/commit/99067d5c944e7bd29a8702689f470f623723f4e7.patch Then configure using meson with -Dc_args="-Wuse-after-free=3" --buildtype=release Compiling with gcc-12 or gcc-13 should give you the warning that looks as follows: [713/2349] Compiling C object src/backend/postgres_lib.a.p/commands_tablecmds.c.o ../src/backend/commands/tablecmds.c: In function ‘ATExecAttachPartition’: ../src/backend/commands/tablecmds.c:18593:25: warning: pointer ‘partBoundConstraint’ may be used after ‘list_concat’ [-Wuse-after-free] 18593 | get_proposed_default_constraint(partBoundConstraint); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ../src/backend/commands/tablecmds.c:18546:26: note: call to ‘list_concat’ here 18546 | partConstraint = list_concat(partBoundConstraint, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 18547 | RelationGetPartitionQual(rel)); | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- Thanks, Amit Langote