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    Subject[PATCH v5 0/9] ipc: Clamp *mni to the real IPCMNI limit & increase that limit
    Date
    v4->v5:
    - Revert the flags back to 16-bit so that there will be no change to
    the size of ctl_table.
    - Enhance the sysctl_check_flags() as requested by Luis to perform more
    checks to spot incorrect ctl_table entries.
    - Change the sysctl selftest to use dummy sysctls instead of production
    ones & enhance it to do more checks.
    - Add one more sysctl selftest for registration failure.
    - Add 2 ipc patches to add an extended mode to increase IPCMNI from
    32k to 2M.
    - Miscellaneous change to incorporate feedback comments from
    reviewers.

    v3->v4:
    - Remove v3 patches 1 & 2 as they have been merged into the mm tree.
    - Change flags from uint16_t to unsigned int.
    - Remove CTL_FLAGS_OOR_WARNED and use pr_warn_ratelimited() instead.
    - Simplify the warning message code.
    - Add a new patch to fail the ctl_table registration with invalid flag.
    - Add a test case for range clamping in sysctl selftest.

    v2->v3:
    - Fix kdoc comment errors.
    - Incorporate comments and suggestions from Luis R. Rodriguez.
    - Add a patch to fix a typo error in fs/proc/proc_sysctl.c.

    v1->v2:
    - Add kdoc comments to the do_proc_do{u}intvec_minmax_conv_param
    structures.
    - Add a new flags field to the ctl_table structure for specifying
    whether range clamping should be activated instead of adding new
    sysctl parameter handlers.
    - Clamp the semmni value embedded in the multi-values sem parameter.

    v1 patch: https://lkml.org/lkml/2018/2/19/453
    v2 patch: https://lkml.org/lkml/2018/2/27/627
    v3 patch: https://lkml.org/lkml/2018/3/1/716
    v4 patch: https://lkml.org/lkml/2018/3/12/867

    The sysctl parameters msgmni, shmmni and semmni have an inherent limit
    of IPC_MNI (32k). However, users may not be aware of that because they
    can write a value much higher than that without getting any error or
    notification. Reading the parameters back will show the newly written
    values which are not real.

    Enforcing the limit by failing sysctl parameter write, however, may
    cause regressions if existing user setup scripts set those parameters
    above 32k as those scripts will now fail in this case.

    To address this delemma, a new flags field is introduced into
    the ctl_table. The value CTL_FLAGS_CLAMP_RANGE can be added to any
    ctl_table entries to enable a looser range clamping without returning
    any error. For example,

    .flags = CTL_FLAGS_CLAMP_RANGE,

    This flags value are now used for the range checking of shmmni,
    msgmni and semmni without breaking existing applications. If any out
    of range value is written to those sysctl parameters, the following
    warning will be printed instead.

    sysctl: "shmmni" was set out of range [0, 32768], clamped to 32768.

    Reading the values back will show 32768 instead of some fake values.

    New sysctl selftests are added to exercise new code added by this
    patchset.

    There are users out there requesting increase in the IPCMNI value.
    The last 2 patches attempt to do that by using a boot kernel parameter
    "ipcmni_extend" to increase the IPCMNI limit from 32k to 2M.

    Eric Biederman had posted an RFC patch to just scrap the IPCMNI limit
    and open up the whole positive integer space for IPC IDs. A major
    issue that I have with this approach is that SysV IPC had been in use
    for over 20 years. We just don't know if there are user applications
    that have dependency on the way that the IDs are built. So drastic
    change like this may have the potential of breaking some applications.

    I prefer a more conservative approach where users will observe no
    change in behavior unless they explictly opt in to enable the extended
    mode. I could open up the whole positive integer space in this case
    like what Eric did, but that will make the code more complex. So I
    just extend IPCMNI to 2M in this case and keep similar ID generation
    logic.

    Waiman Long (9):
    sysctl: Add flags to support min/max range clamping
    proc/sysctl: Provide additional ctl_table.flags checks
    sysctl: Warn when a clamped sysctl parameter is set out of range
    ipc: Clamp msgmni and shmmni to the real IPCMNI limit
    ipc: Clamp semmni to the real IPCMNI limit
    test_sysctl: Add range clamping test
    test_sysctl: Add ctl_table registration failure test
    ipc: Allow boot time extension of IPCMNI from 32k to 2M
    ipc: Conserve sequence numbers in extended IPCMNI mode

    Documentation/admin-guide/kernel-parameters.txt | 3 +
    fs/proc/proc_sysctl.c | 62 ++++++++++++++++++++
    include/linux/ipc.h | 11 +++-
    include/linux/ipc_namespace.h | 1 +
    include/linux/sysctl.h | 32 +++++++++++
    ipc/ipc_sysctl.c | 33 ++++++++++-
    ipc/sem.c | 25 ++++++++
    ipc/util.c | 41 ++++++++-----
    ipc/util.h | 23 +++++---
    kernel/sysctl.c | 76 ++++++++++++++++++++++---
    lib/test_sysctl.c | 70 +++++++++++++++++++++++
    tools/testing/selftests/sysctl/sysctl.sh | 67 ++++++++++++++++++++++
    12 files changed, 411 insertions(+), 33 deletions(-)

    --
    1.8.3.1

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