Ensure length(ipiv)==n before calling LAPACK.getrs! to avoid segfaults (#49602)

Author: aravindh-krishnamoorthy

stdlib/LinearAlgebra/src/lapack.jl

@@ -1010,6 +1010,9 @@ for (gels, gesv, getrs, getri, elty) in
             if n != size(B, 1)
                 throw(DimensionMismatch("B has leading dimension $(size(B,1)), but needs $n"))
             end
+            if n != length(ipiv)
+                throw(DimensionMismatch("ipiv has length $(length(ipiv)), but needs to be $n"))
+            end
             nrhs = size(B, 2)
             info = Ref{BlasInt}()
             ccall((@blasfunc($getrs), libblastrampoline), Cvoid,

stdlib/LinearAlgebra/test/lapack.jl

@@ -720,4 +720,13 @@ a = zeros(2,0), zeros(0)
 @test LinearAlgebra.LAPACK.geqrf!(a...) === a
 @test LinearAlgebra.LAPACK.gerqf!(a...) === a
 
+# Issue #49489: https://github.com/JuliaLang/julia/issues/49489
+# Dimension mismatch between A and ipiv causes segfaults
+@testset "issue #49489" begin
+    A = randn(23,23)
+    b = randn(23)
+    ipiv = collect(1:20)
+    @test_throws DimensionMismatch LinearAlgebra.LAPACK.getrs!('N', A, ipiv, b)
+end
+
 end # module TestLAPACK