mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-04-30 20:30:32 -04:00
077ce028b8
pscsi_map_sg() uses the variable nr_pages as a hint for bio_kmalloc() how many vector elements to allocate. If nr_pages is < BIO_MAX_PAGES, it will be reset to 0 after successful allocation of the bio. If bio_add_pc_page() fails later for whatever reason, pscsi_map_sg() tries to allocate another bio, passing nr_vecs = 0. This causes bio_add_pc_page() to fail immediately in the next call. pci_map_sg() continues to allocate zero-length bios until memory is exhausted and the kernel crashes with OOM. This can be easily observed by exporting a SATA DVD drive via pscsi. The target crashes as soon as the client tries to access the DVD LUN. In the case I analyzed, bio_add_pc_page() would fail because the DVD device's max_sectors_kb (128) was exceeded. Avoid this by simply not resetting nr_pages to 0 after allocating the bio. This way, the client receives an I/O error when it tries to send requests exceeding the devices max_sectors_kb, and eventually gets it right. The client must still limit max_sectors_kb e.g. by an udev rule if (like in my case) the driver doesn't report valid block limits, otherwise it encounters I/O errors. Link: https://lore.kernel.org/r/20210323212431.15306-1-mwilck@suse.com Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Lee Duncan <lduncan@suse.com> Signed-off-by: Martin Wilck <mwilck@suse.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.