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relay: fix for possible loss/corruption of produced subbufs

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Fix possible loss/corruption of produced subbufs in
relay_subbufs_consumed().

When buf->subbufs_produced wraps around after UINT_MAX and
buf->subbufs_consumed is still < UINT_MAX, the condition

	if (buf->subbufs_consumed > buf->subbufs_produced)

will be true even for certain valid values of subbufs_consumed.  This may
lead to loss or corruption of produced subbufs.

Signed-off-by: Aravind Srinivasan <raa.aars@gmail.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Tom Zanussi <zanussi@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Aravind Srinivasan 2009-04-02 16:58:59 -07:00 committed by Linus Torvalds
parent edb79a2132
commit 2c53d9109f
1 changed files with 5 additions and 3 deletions
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8
kernel/relay.c
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@ -797,13 +797,15 @@ void relay_subbufs_consumed(struct rchan *chan,
if (!chan)
return;
if (cpu >= NR_CPUS || !chan->buf[cpu])
if (cpu >= NR_CPUS || !chan->buf[cpu] ||
subbufs_consumed > chan->n_subbufs)
return;
buf = chan->buf[cpu];
buf->subbufs_consumed += subbufs_consumed;
if (buf->subbufs_consumed > buf->subbufs_produced)
if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
buf->subbufs_consumed = buf->subbufs_produced;
else
buf->subbufs_consumed += subbufs_consumed;
}
EXPORT_SYMBOL_GPL(relay_subbufs_consumed);