src/patches/suse-2.6.27.39/patches.fixes/taskstats-align

   1 From: Jeff Mahoney <jeffm@suse.com>
   2 Subject: [PATCH] delayacct: align to 8 byte boundary on 64-bit systems
   3 References: bnc#492547 bnc#448410
   4
   5  prepare_reply sets up an skb for the response. If I understand it correctly,
   6  the payload contains:
   7
   8  +--------------------------------+
   9  | genlmsghdr - 4 bytes           |
  10  +--------------------------------+
  11  | NLA header - 4 bytes           | /* Aggregate header */
  12  +-+------------------------------+
  13  | | NLA header - 4 bytes         | /* PID header */
  14  | +------------------------------+
  15  | | pid/tgid   - 4 bytes         |
  16  | +------------------------------+
  17  | | NLA header - 4 bytes         | /* stats header */
  18  | + -----------------------------+ <- oops. aligned on 4 byte boundary
  19  | | struct taskstats - 328 bytes |
  20  +-+------------------------------+
  21
  22  The start of the taskstats struct must be 8 byte aligned on IA64 (and other
  23  systems with 8 byte alignment rules for 64-bit types) or runtime alignment
  24  warnings will be issued.
  25
  26  This patch pads the pid/tgid field out to sizeof(long), which forces
  27  the alignment of taskstats. The getdelays userspace code is ok with this
  28  since it assumes 32-bit pid/tgid and then honors that header's length field.
  29
  30  An array is used to avoid exposing kernel memory contents to userspace in the
  31  response.
  32
  33 Signed-off-by: Jeff Mahoney <jeffm@suse.com>
  34 ---
  35  kernel/taskstats.c |    8 +++++++-
  36  1 file changed, 7 insertions(+), 1 deletion(-)
  37
  38 --- a/kernel/taskstats.c
  39 +++ b/kernel/taskstats.c
  40 @@ -362,6 +362,12 @@ static struct taskstats *mk_reply(struct
  41         struct nlattr *na, *ret;
  42         int aggr;
  43
  44 +       /* If we don't pad, we end up with alignment on a 4 byte boundary.
  45 +        * This causes lots of runtime warnings on systems requiring 8 byte
  46 +        * alignment */
  47 +       u32 pids[2] = { pid, 0 };
  48 +       int pid_size = ALIGN(sizeof(pid), sizeof(long));
  49 +
  50         aggr = (type == TASKSTATS_TYPE_PID)
  51                         ? TASKSTATS_TYPE_AGGR_PID
  52                         : TASKSTATS_TYPE_AGGR_TGID;
  53 @@ -369,7 +375,7 @@ static struct taskstats *mk_reply(struct
  54         na = nla_nest_start(skb, aggr);
  55         if (!na)
  56                 goto err;
  57 -       if (nla_put(skb, type, sizeof(pid), &pid) < 0)
  58 +       if (nla_put(skb, type, pid_size, pids) < 0)
  59                 goto err;
  60         ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats));
  61         if (!ret)