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| author | Jeff Mahoney <jeffm@suse.com> | 2010-10-27 15:34:43 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-10-27 18:03:17 -0700 |
| commit | 85893120699f8bae8caa12a8ee18ab5fceac978e (patch) | |
| tree | 07fb62d6c8818e8feab72d4bd78b3e4a2bbbb829 | |
| parent | db9e5679d6aecb17253f41bd06d98194800f9c01 (diff) | |
| download | lwn-85893120699f8bae8caa12a8ee18ab5fceac978e.tar.gz lwn-85893120699f8bae8caa12a8ee18ab5fceac978e.zip | |
delayacct: align to 8 byte boundary on 64-bit systems
prepare_reply() sets up an skb for the response. The payload contains:
+--------------------------------+
| genlmsghdr - 4 bytes |
+--------------------------------+
| NLA header - 4 bytes | /* Aggregate header */
+-+------------------------------+
| | NLA header - 4 bytes | /* PID header */
| +------------------------------+
| | pid/tgid - 4 bytes |
| +------------------------------+
| | NLA header - 4 bytes | /* stats header */
| + -----------------------------+ <- oops. aligned on 4 byte boundary
| | struct taskstats - 328 bytes |
+-+------------------------------+
The start of the taskstats struct must be 8 byte aligned on IA64 (and
other systems with 8 byte alignment rules for 64-bit types) or runtime
alignment warnings will be issued.
This patch pads the pid/tgid field out to sizeof(long), which forces the
alignment of taskstats. The getdelays userspace code is ok with this
since it assumes 32-bit pid/tgid and then honors that header's length
field.
An array is used to avoid exposing kernel memory contents to userspace in
the response.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | kernel/taskstats.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/taskstats.c b/kernel/taskstats.c index 11281d5792bd..5a651aa63d61 100644 --- a/kernel/taskstats.c +++ b/kernel/taskstats.c @@ -360,6 +360,12 @@ static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid) struct nlattr *na, *ret; int aggr; + /* If we don't pad, we end up with alignment on a 4 byte boundary. + * This causes lots of runtime warnings on systems requiring 8 byte + * alignment */ + u32 pids[2] = { pid, 0 }; + int pid_size = ALIGN(sizeof(pid), sizeof(long)); + aggr = (type == TASKSTATS_TYPE_PID) ? TASKSTATS_TYPE_AGGR_PID : TASKSTATS_TYPE_AGGR_TGID; @@ -367,7 +373,7 @@ static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid) na = nla_nest_start(skb, aggr); if (!na) goto err; - if (nla_put(skb, type, sizeof(pid), &pid) < 0) + if (nla_put(skb, type, pid_size, pids) < 0) goto err; ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats)); if (!ret) |