rust: dma: return zero for Coherent reads past EOF

Coherent<T>::write_to_slice() calculates a zero-byte copy when the file
offset is beyond the allocation, but still calls
UserSliceWriter::write_dma(). The latter rejects offsets beyond the
allocation even when the copy length is zero, so a debugfs read past EOF
returns -ERANGE.

Return before calling write_dma() when the offset is at or beyond the
allocation, matching simple_read_from_buffer() EOF semantics.

Fixes: 016818513936 ("rust: dma: implement BinaryWriter for Coherent<[u8]>")
Cc: stable@vger.kernel.org
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/291566-Library/topic/.E2.9C.94.20Possible.20past-EOF.20bug.20in.20Coherent.3CT.3E.3A.3Awrite_to_slice/near/611677095
Signed-off-by: Younes Akhouayri <git@younes.io>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Onur Özkan <work@onurozkan.dev>
Link: https://patch.msgid.link/20260730-fix-dma-coherent-eof-v2-1-8aff21054afa@younes.io
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

0 files changed, 0 insertions, 0 deletions