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A kernel memory leak was identified by the 'ioctl_sg01' test from Linux
Test Project (LTP). The following bytes were mainly observed: 0x53425355.
When USB storage devices incorrectly skip the data phase with status data,
the code extracts/validates the CSW from the sg buffer, but fails to clear
it afterwards. This leaves status protocol data in srb's transfer buffer,
such as the US_BULK_CS_SIGN 'USBS' signature observed here. Thus, this can
lead to USB protocols leaks to user space through SCSI generic (/dev/sg*)
interfaces, such as the one seen here when the LTP test requested 512 KiB.
Fix the leak by zeroing the CSW data in srb's transfer buffer immediately
after the validation of devices that skip data phase.
Note: Differently from CVE-2018-1000204, which fixed a big leak by zero-
ing pages at allocation time, this leak occurs after allocation, when USB
protocol data is written to already-allocated sg pages.
Fixes: a45b599ad8 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()")
Cc: stable <stable@kernel.org>
Signed-off-by: Desnes Nunes <desnesn@redhat.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://patch.msgid.link/20251031043436.55929-1-desnesn@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 reStructuredText 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.