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[Fix] Provided MPI_type_get_content array sizes may exceed actual ones, do not use them #13131

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[Fix] Provided MPI_type_get_content array sizes may exceed actual ones, do not use them #13131

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10 changes: 9 additions & 1 deletion ompi/mpi/c/type_get_contents.c
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@
* All rights reserved.
* Copyright (c) 2015 Research Organization for Information Science
* and Technology (RIST). All rights reserved.
* Copyright (c) 2025 BULL S.A.S. All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
Expand Down Expand Up @@ -45,7 +46,7 @@ int MPI_Type_get_contents(MPI_Datatype mtype,
MPI_Aint array_of_addresses[],
MPI_Datatype array_of_datatypes[])
{
int rc, i;
int rc, i, type_code;
MPI_Datatype newtype;

MEMCHECKER(
Expand All @@ -65,6 +66,13 @@ int MPI_Type_get_contents(MPI_Datatype mtype,
}
}

/* Counts may exceed actual ones, we have no choice but to recompute them */
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Not sure I understand that comment: what are the actual ones? The count argument the user provided? Or the

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/* Counts may exceed actual ones, we have no choice but to recompute them */
/* Counts may exceed the user-provided counts, we have no choice but to recompute them */

rc = ompi_datatype_get_args(mtype, 0, &max_integers, NULL, &max_addresses, NULL, &max_datatypes,
NULL, &type_code);
if (rc != MPI_SUCCESS) {
OMPI_ERRHANDLER_RETURN(MPI_ERR_INTERN, MPI_COMM_WORLD, MPI_ERR_INTERN, FUNC_NAME);
}

Comment on lines +70 to +75
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What is the point of querying the sizes if we don't act on that information? If the user told us the arrays are of a certain size and the type requires more then we should error out, raising MPI_ERR_ARG.

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This updates the user provided max lengths before passing them to ompi_datatype_get_args. As if ompi_datatype_get_args was not correctly handling the case where user provides more space than required (which is not the case as I pointed in my prior comment).

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I'd be worried about the converse: the user provides insufficient space and we write past the bounds of the user buffer. That is what I thought this patch addressed. Otherwise I don't see what this patch accomplishes.

rc = ompi_datatype_get_args( mtype, 1, &max_integers, array_of_integers,
&max_addresses, array_of_addresses,
&max_datatypes, array_of_datatypes, NULL );
Expand Down