From: Greg KH <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org,
alan@lxorguk.ukuu.org.uk, Peter Zijlstra <a.p.zijlstra@chello.nl>,
Ilya Tumaykin <librarian_rus@yahoo.com>,
Wu Fengguang <fengguang.wu@intel.com>
Subject: [05/15] lib: proportion: lower PROP_MAX_SHIFT to 32 on 64-bit kernel
Date: Thu, 16 Feb 2012 16:55:14 -0800 [thread overview]
Message-ID: <20120217005510.559345291@linuxfoundation.org> (raw)
In-Reply-To: <20120217005650.GA17119@kroah.com>
3.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Wu Fengguang <fengguang.wu@intel.com>
commit 3310225dfc71a35a2cc9340c15c0e08b14b3c754 upstream.
PROP_MAX_SHIFT should be set to <=32 on 64-bit box. This fixes two bugs
in the below lines of bdi_dirty_limit():
bdi_dirty *= numerator;
do_div(bdi_dirty, denominator);
1) divide error: do_div() only uses the lower 32 bit of the denominator,
which may trimmed to be 0 when PROP_MAX_SHIFT > 32.
2) overflow: (bdi_dirty * numerator) could easily overflow if numerator
used up to 48 bits, leaving only 16 bits to bdi_dirty
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reported-by: Ilya Tumaykin <librarian_rus@yahoo.com>
Tested-by: Ilya Tumaykin <librarian_rus@yahoo.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/proportions.h | 4 ++++
1 file changed, 4 insertions(+)
--- a/include/linux/proportions.h
+++ b/include/linux/proportions.h
@@ -81,7 +81,11 @@ void prop_inc_percpu(struct prop_descrip
* Limit the time part in order to ensure there are some bits left for the
* cycle counter and fraction multiply.
*/
+#if BITS_PER_LONG == 32
#define PROP_MAX_SHIFT (3*BITS_PER_LONG/4)
+#else
+#define PROP_MAX_SHIFT (BITS_PER_LONG/2)
+#endif
#define PROP_FRAC_SHIFT (BITS_PER_LONG - PROP_MAX_SHIFT - 1)
#define PROP_FRAC_BASE (1UL << PROP_FRAC_SHIFT)
next prev parent reply other threads:[~2012-02-17 0:55 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-17 0:56 [00/15] 3.0.22-stable review Greg KH
2012-02-17 0:55 ` [01/15] perf evsel: Fix an issue where perf report fails to show the proper percentage Greg KH
2012-02-17 0:55 ` [02/15] perf tools: Fix perf stack to non executable on x86_64 Greg KH
2012-02-17 0:55 ` [03/15] drm/i915: no lvds quirk for AOpen MP45 Greg KH
2012-02-17 0:55 ` [04/15] hwmon: (f75375s) Fix bit shifting in f75375_write16 Greg KH
2012-02-17 0:55 ` Greg KH [this message]
2012-02-17 0:55 ` [06/15] relay: prevent integer overflow in relay_open() Greg KH
2012-02-17 0:55 ` [07/15] mac80211: timeout a single frame in the rx reorder buffer Greg KH
2012-02-17 0:55 ` [08/15] writeback: fix dereferencing NULL bdi->dev on trace_writeback_queue Greg KH
2012-02-17 0:55 ` [09/15] gpio/pca953x: Fix warning of enabled interrupts in handler Greg KH
2012-02-17 0:55 ` [10/15] hwmon: (f75375s) Fix automatic pwm mode setting for F75373 & F75375 Greg KH
2012-02-17 0:55 ` [11/15] crypto: sha512 - Use binary and instead of modulus Greg KH
2012-02-17 0:55 ` Greg KH
2012-02-17 0:55 ` [12/15] crypto: sha512 - Avoid stack bloat on i386 Greg KH
2012-02-17 0:55 ` Greg KH
2012-02-17 0:55 ` [13/15] ALSA: intel8x0: Fix default inaudible sound on Gateway M520 Greg KH
2012-02-17 0:55 ` [14/15] xen pvhvm: do not remap pirqs onto evtchns if !xen_have_vector_callback Greg KH
2012-02-17 0:55 ` [15/15] slub: fix a possible memleak in __slab_alloc() Greg KH
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