Eric Lee / smarc-fsl-linux-kernel

02 Nov, 2017

1 commit

  • b24413180   License cleanup: add SPDX GPL-2.0 license identifier to files with no license ... Browse Code »

    Many source files in the tree are missing licensing information, which
    makes it harder for compliance tools to determine the correct license.

    By default all files without license information are under the default
    license of the kernel, which is GPL version 2.

    Update the files which contain no license information with the 'GPL-2.0'
    SPDX license identifier. The SPDX identifier is a legally binding
    shorthand, which can be used instead of the full boiler plate text.

    This patch is based on work done by Thomas Gleixner and Kate Stewart and
    Philippe Ombredanne.

    How this work was done:

    Patches were generated and checked against linux-4.14-rc6 for a subset of
    the use cases:
    - file had no licensing information it it.
    - file was a */uapi/* one with no licensing information in it,
    - file was a */uapi/* one with existing licensing information,

    Further patches will be generated in subsequent months to fix up cases
    where non-standard license headers were used, and references to license
    had to be inferred by heuristics based on keywords.

    The analysis to determine which SPDX License Identifier to be applied to
    a file was done in a spreadsheet of side by side results from of the
    output of two independent scanners (ScanCode & Windriver) producing SPDX
    tag:value files created by Philippe Ombredanne. Philippe prepared the
    base worksheet, and did an initial spot review of a few 1000 files.

    The 4.13 kernel was the starting point of the analysis with 60,537 files
    assessed. Kate Stewart did a file by file comparison of the scanner
    results in the spreadsheet to determine which SPDX license identifier(s)
    to be applied to the file. She confirmed any determination that was not
    immediately clear with lawyers working with the Linux Foundation.

    Criteria used to select files for SPDX license identifier tagging was:
    - Files considered eligible had to be source code files.
    - Make and config files were included as candidates if they contained >5
    lines of source
    - File already had some variant of a license header in it (even if
    Reviewed-by: Philippe Ombredanne
    Reviewed-by: Thomas Gleixner
    Signed-off-by: Greg Kroah-Hartman

    Greg Kroah-Hartman
     

14 Feb, 2017

1 commit

  • 03a9e24ef   md linear: fix a race between linear_add() and linear_congested() ... Browse Code »

    Recently I receive a bug report that on Linux v3.0 based kerenl, hot add
    disk to a md linear device causes kernel crash at linear_congested(). From
    the crash image analysis, I find in linear_congested(), mddev->raid_disks
    contains value N, but conf->disks[] only has N-1 pointers available. Then
    a NULL pointer deference crashes the kernel.

    There is a race between linear_add() and linear_congested(), RCU stuffs
    used in these two functions cannot avoid the race. Since Linuv v4.0
    RCU code is replaced by introducing mddev_suspend(). After checking the
    upstream code, it seems linear_congested() is not called in
    generic_make_request() code patch, so mddev_suspend() cannot provent it
    from being called. The possible race still exists.

    Here I explain how the race still exists in current code. For a machine
    has many CPUs, on one CPU, linear_add() is called to add a hard disk to a
    md linear device; at the same time on other CPU, linear_congested() is
    called to detect whether this md linear device is congested before issuing
    an I/O request onto it.

    Now I use a possible code execution time sequence to demo how the possible
    race happens,

    seq linear_add() linear_congested()
    0 conf=mddev->private
    1 oldconf=mddev->private
    2 mddev->raid_disks++
    3 for (i=0; iraid_disks;i++)
    4 bdev_get_queue(conf->disks[i].rdev->bdev)
    5 mddev->private=newconf

    In linear_add() mddev->raid_disks is increased in time seq 2, and on
    another CPU in linear_congested() the for-loop iterates conf->disks[i] by
    the increased mddev->raid_disks in time seq 3,4. But conf with one more
    element (which is a pointer to struct dev_info type) to conf->disks[] is
    not updated yet, accessing its structure member in time seq 4 will cause a
    NULL pointer deference fault.

    To fix this race, there are 2 parts of modification in the patch,
    1) Add 'int raid_disks' in struct linear_conf, as a copy of
    mddev->raid_disks. It is initialized in linear_conf(), always being
    consistent with pointers number of 'struct dev_info disks[]'. When
    iterating conf->disks[] in linear_congested(), use conf->raid_disks to
    replace mddev->raid_disks in the for-loop, then NULL pointer deference
    will not happen again.
    2) RCU stuffs are back again, and use kfree_rcu() in linear_add() to
    free oldconf memory. Because oldconf may be referenced as mddev->private
    in linear_congested(), kfree_rcu() makes sure that its memory will not
    be released until no one uses it any more.
    Also some code comments are added in this patch, to make this modification
    to be easier understandable.

    This patch can be applied for kernels since v4.0 after commit:
    3be260cc18f8 ("md/linear: remove rcu protections in favour of
    suspend/resume"). But this bug is reported on Linux v3.0 based kernel, for
    people who maintain kernels before Linux v4.0, they need to do some back
    back port to this patch.

    Changelog:
    - V3: add 'int raid_disks' in struct linear_conf, and use kfree_rcu() to
    replace rcu_call() in linear_add().
    - v2: add RCU stuffs by suggestion from Shaohua and Neil.
    - v1: initial effort.

    Signed-off-by: Coly Li
    Cc: Shaohua Li
    Cc: Neil Brown
    Cc: stable@vger.kernel.org
    Signed-off-by: Shaohua Li

    colyli@suse.de
     

11 Oct, 2011

3 commits

25 Aug, 2011

1 commit

18 Jun, 2009

1 commit

  • 495d35730   md/linear: use call_rcu to free obsolete 'conf' structures. ... Browse Code »

    Current, when we update the 'conf' structure, when adding a
    drive to a linear array, we keep the old version around until
    the array is finally stopped, as it is not safe to free it
    immediately.

    Now that we have rcu protection on all accesses to 'conf',
    we can use call_rcu to free it more promptly.

    Signed-off-by: NeilBrown

    NeilBrown
     

16 Jun, 2009

3 commits

31 Mar, 2009

2 commits