kernel/linux.git/drivers/comedi/comedi_buf.c, branch v6.18.21

comedi: fix divide-by-zero in comedi_buf_munge()

2025-10-22T06:03:52+00:00

The comedi_buf_munge() function performs a modulo operation `async->munge_chan %= async->cmd.chanlist_len` without first checking if chanlist_len is zero. If a user program submits a command with chanlist_len set to zero, this causes a divide-by-zero error when the device processes data in the interrupt handler path. Add a check for zero chanlist_len at the beginning of the function, similar to the existing checks for !map and CMDF_RAWDATA flag. When chanlist_len is zero, update munge_count and return early, indicating the data was handled without munging. This prevents potential kernel panics from malformed user commands. Reported-by: syzbot+f6c3c066162d2c43a66c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=f6c3c066162d2c43a66c Cc: stable@vger.kernel.org Signed-off-by: Deepanshu Kartikey Reviewed-by: Ian Abbott Link: https://patch.msgid.link/20250924102639.1256191-1-kartikey406@gmail.com Signed-off-by: Greg Kroah-Hartman

comedi: allocate DMA coherent buffer as individual pages

2025-04-25T13:53:19+00:00

Depending on the driver, the acquisition buffer is allocated either from normal memory, or from DMA coherent memory. For normal memory, the buffer is allocated as individual pages, but for DMA coherent memory, it is allocated as a single block. Prior to commit e36472145aa7 ("staging: comedi: use dma_mmap_coherent for DMA-able buffer mmap"), the buffer was allocated as individual pages for DMA coherent memory too, but that was changed to allocate it as a single block to allow `dma_mmap_coherent()` to be used to mmap it, because that requires the pages being mmap'ed to be contiguous. This patch allocates the buffer from DMA coherent memory a page at a time again, and works around the limitation of `dma_mmap_coherent()` by calling it in a loop for each page, with temporarily modified `vm_start` and `vm_end` values in the VMA. (The `vm_pgoff` value is 0.) Cc: Christoph Hellwig Signed-off-by: Ian Abbott Link: https://lore.kernel.org/r/20250415114008.5977-5-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman

comedi: remove the mapping of the Comedi buffer in vmalloc address space

2025-04-25T13:53:19+00:00

Now that all the code that accesses the Comedi buffer data does so page-by-page, using the `virt_addr` member of `struct comedi_buf_page` to point to the data of each page, do not linearly map the buffer into vmalloc address space (pointed to by the `prealloc_buf` member of `struct comedi_async`). That was only done for convenience, but was not done for those drivers that need a DMA coherent buffer, which is allocated in a single chunk. Remove the `prealloc_buf` member as it is no longer used. Signed-off-by: Ian Abbott Link: https://lore.kernel.org/r/20250415114008.5977-4-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman

comedi: access buffer data page-by-page

2025-04-25T13:53:18+00:00

The aim is to get rid of the `prealloc_buf` member of `struct comedi_async` and access the buffer contents on a page-by-page basis using the addresses in the `virt_addr` member of `struct comedi_buf_page`. This will allow us to eliminate a `vmap()` that maps the whole buffer. Since the buffer pages have non-consecutive `virt_addr` addresses in virtual memory (except for drivers using DMA), change the loops that access buffer data to access it page-by-page. Signed-off-by: Ian Abbott Link: https://lore.kernel.org/r/20250415114008.5977-3-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman

comedi: Move the main COMEDI headers

2021-11-26T15:48:59+00:00

Move the main COMEDI driver headers out of "drivers/comedi/" into new directory "include/linux/comedi/". These are "comedidev.h", "comedilib.h", "comedi_pci.h", "comedi_pcmcia.h", and "comedi_usb.h". Additionally, move the user-space API header "comedi.h" into "include/uapi/linux/" and add "WITH Linux-syscall-note" to its SPDX-License-Identifier. Update the "COMEDI DRIVERS" section of the MAINTAINERS file to account for these changes. Signed-off-by: Ian Abbott Link: https://lore.kernel.org/r/20211117120604.117740-2-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman

staging: comedi: move out of staging directory

2021-04-15T07:26:25+00:00

The comedi code came into the kernel back in 2008, but traces its lifetime to much much earlier. It's been polished and buffed and there's really nothing preventing it from being part of the "real" portion of the kernel. So move it to drivers/comedi/ as it belongs there. Many thanks to the hundreds of developers who did the work to make this happen. Cc: Ian Abbott Cc: H Hartley Sweeten Link: https://lore.kernel.org/r/YHauop4u3sP6lz8j@kroah.com Signed-off-by: Greg Kroah-Hartman