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    SubjectRe: [PATCH 1/2] treewide: fix memory corruptions when TASK_COMM_LEN != 16
    On Sat, 21 Jan 2012 23:09:44 +0100
    Jan Engelhardt <> wrote:

    > I found that the kernel BUG()s out, already during boot, when bumping
    > TASK_COMM_LEN to a value larger than 16

    We can never increase TASK_COMM_LEN - it is part of the kernel ABI/API.
    Doing so would destroy existing userspace which uses 16-byte buffers.

    > (and I can imagine the same
    > problem unfolding as well if it is set to something smaller).

    hm, that's a surprise. Decreasing TASK_COMM_LEN is at least slightly
    possible but it's hard to see why we should do so.

    > Various places do insufficient length checks, simply assume certain
    > sizes or hardcode things. Even though e.g. get_task_comm clearly
    > documents that its buffer ought to be TASK_COMM_LEN long, I do believe
    > that an extra size parameter, such as added in this patch, is a lot
    > more robust than relying on callers getting the buffer size right.
    > With this patch, I no longer experience crashes, but that is not to
    > say that there are not any further places (e.g. in modules I never
    > use) with flakey ->comm handling.

    You do seem to have found a few warts around the task->comm handling.
    But I don't believe that addressing them justifies adding new code
    (adding another argument to get_task_comm).

    If you're interested in working on this stuff I'd suggest that we
    confine ourselves to cleaning things up (without adding code) rather
    than permitting a different TASK_COMM_LEN. Things like replacing "16"
    with TASK_COMM_LEN.

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