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begin_cpu_udmabuf() maps the sg_table with the caller-provided direction
(e.g., DMA_TO_DEVICE for a write-only sync), and caches it in ubuf->sg
for reuse. However, release_udmabuf() always unmaps this sg_table with
a hardcoded DMA_BIDIRECTIONAL, regardless of the direction that was
originally used for the mapping.
With CONFIG_DMA_API_DEBUG=y this produces:
DMA-API: misc udmabuf: device driver frees DMA memory with different
direction [device address=0x000000044a123000] [size=4096 bytes]
[mapped with DMA_TO_DEVICE] [unmapped with DMA_BIDIRECTIONAL]
The issue was found during video playback when GStreamer performed a
write-only DMA_BUF_IOCTL_SYNC on a udmabuf. It can be reproduced
with CONFIG_DMA_API_DEBUG=y by creating a udmabuf from a memfd,
performing a write-only sync (DMA_BUF_SYNC_WRITE without
DMA_BUF_SYNC_READ), and closing the file descriptor.
Fix this by storing the DMA direction used when the sg_table is first
created in begin_cpu_udmabuf(), and passing that same direction to
put_sg_table() in release_udmabuf().
Fixes:
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. 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