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    Subject[PATCH] kmsg: limit message size
    There are no size checks in kmsg_write(), and we try allocating enough
    memory to store everything userspace gave us, which may be too much for
    kmalloc to allocate.

    Furthermore, we can have an integer overflow if len==INT_MAX, in that case
    we'll corrupt kernel memory.

    This was tested with several userspace programs that write to kmsg, and haven't
    found a case where the program attempts to write more than PAGE_SIZE.

    Signed-off-by: Sasha Levin <>
    drivers/char/mem.c | 3 +++
    1 files changed, 3 insertions(+), 0 deletions(-)

    diff --git a/drivers/char/mem.c b/drivers/char/mem.c
    index d6e9d08..c90964b 100644
    --- a/drivers/char/mem.c
    +++ b/drivers/char/mem.c
    @@ -815,6 +815,9 @@ static ssize_t kmsg_writev(struct kiocb *iocb, const struct iovec *iv,
    ssize_t ret = -EFAULT;
    size_t len = iov_length(iv, count);

    + if (len > PAGE_SIZE)
    + return -E2BIG;
    line = kmalloc(len + 1, GFP_KERNEL);
    if (line == NULL)
    return -ENOMEM;

     \ /
      Last update: 2012-05-05 17:01    [W:0.020 / U:7.596 seconds]
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