[PATCH 00/38] Fixes related to incorrect usage of unsigned types

[PATCH 00/38] Fixes related to incorrect usage of unsigned types

[Andrzej Hajda]

Hi,

This is set of independent patches. The only connection between
them is that they try to address problems spotted by proposed
coccinelle semantic patch unsigned_lesser_than_zero.cocci[1].

Semantic patch finds comparisons of types:
    unsigned < 0
    unsigned >= 0
The former is always false, the latter is always true.
Such comparisons are useless, so theoretically they could be
safely removed, but their presence quite often indicates bugs.

This patchset contains mainly real bug fixes(patches 01-25),
usually type fixes.

Patches 26-37 removes unnecessary checks. Semantic patch found
much more such places (more than 80), but since every case needs
some analysis I have decided to leave them for antoher patchset.

The last patch should be probably replaced with something better,
I guess it should be treated rather as bug report.

The patches are based on linux-next (20150918).

Patches were only compile tested, so please look at them carefully.

I have sent all patches to linux-kernel mailing list. Individual
patches + cover letter went also to apropriate addresses,
according to get_maintainers.pl script.

One more thing. To fullfill different maintaner/subsystem requirements
I have decided to prefix patch subjects with prefixes present in
last 10 commits for affected files. I am not sure if this is the
best solution, if there are any better solutions please let me know :)

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Regards
Andrzej


Andrzej Hajda (38):
  arm-cci: fix handling cpumask_any_but return value
  bus: arm-ccn: fix handling cpumask_any_but return value
  drm/i915: fix handling gen8_emit_flush_coherentl3_wa result
  IB/ehca: fix handling idr_alloc result
  staging: lustre: fix handling lustre_posix_acl_xattr_filter result
  tty: serial: lpc32xx_hs: fix handling platform_get_irq result
  usb: host: ehci-msm: fix handling platform_get_irq result
  openvswitch: fix handling result of ipv6_skip_exthdr
  selftests/timers: fix write return value handlng
  hwrng: fix handling platform_get_irq
  HSI: omap_ssi: fix handling ida_simple_get result
  HSI: omap_ssi_port: fix handling of_get_named_gpio result
  ARM: shmobile: apmu: correct type of CPU id
  clk: vt8500: fix sign of possible PLL values
  drm/layerscape: fix handling fsl_dcu_drm_plane_index result
  gpu: ipu-v3: fix div_ratio type
  isdn: hisax: fix frame calculation
  net/ibm/emac: fix type of phy_mode
  net: stmmac: fix type of entry variable
  net: brcm80211: fix range check
  mwifiex: fix comparison expression
  orinoco: fix checking for default value
  rndis_wlan: fix checking for default value
  rtc: opal: fix type of token
  staging: media: davinci_vpfe: fix ipipe_mode type
  staging: lustre: remove invalid check
  usbnet: remove invalid check
  video/omap: remove invalid check
  Input: touchscreen: atmel: remove invalid check
  leds: flash: remove invalid check
  leds: tca6507: remove invalid check
  fs/cachefiles: remove invalid checks
  mm/memblock.c: remove invalid check
  perf: remove invalid check
  ptrace: remove invalid check
  MIPS: remove invalid check
  zlib_deflate/deftree: change always true condition to 1
  drm/radeon: simplify boot level calculation

 arch/arm/mach-shmobile/platsmp-apmu.c               |  2 +-
 arch/mips/mm/sc-mips.c                              |  4 ++--
 arch/sh/kernel/ptrace_32.c                          |  3 +--
 arch/sh/kernel/ptrace_64.c                          |  4 ++--
 drivers/bus/arm-cci.c                               |  2 +-
 drivers/bus/arm-ccn.c                               |  2 +-
 drivers/char/hw_random/xgene-rng.c                  |  7 ++++---
 drivers/clk/clk-vt8500.c                            |  6 +++---
 drivers/gpu/drm/amd/amdgpu/kv_dpm.c                 | 11 +----------
 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_plane.c         |  3 ++-
 drivers/gpu/drm/i915/intel_lrc.c                    |  7 ++++---
 drivers/gpu/drm/radeon/kv_dpm.c                     | 11 +----------
 drivers/gpu/ipu-v3/ipu-csi.c                        |  2 +-
 drivers/hsi/controllers/omap_ssi.c                  |  7 +++----
 drivers/hsi/controllers/omap_ssi_port.c             |  8 ++++----
 drivers/input/touchscreen/atmel_mxt_ts.c            |  2 +-
 drivers/isdn/hisax/hfc4s8s_l1.c                     | 10 +++++-----
 drivers/leds/led-class-flash.c                      |  2 +-
 drivers/leds/leds-tca6507.c                         |  2 +-
 drivers/net/ethernet/ibm/emac/core.h                |  2 +-
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c   |  2 +-
 drivers/net/usb/lan78xx.c                           |  5 -----
 drivers/net/usb/smsc75xx.c                          |  5 -----
 drivers/net/usb/smsc95xx.c                          |  5 -----
 drivers/net/wireless/brcm80211/brcmsmac/main.c      |  2 +-
 drivers/net/wireless/mwifiex/11n_rxreorder.c        |  4 ++--
 drivers/net/wireless/orinoco/cfg.c                  |  6 +++---
 drivers/net/wireless/rndis_wlan.c                   |  2 +-
 drivers/rtc/rtc-opal.c                              |  4 ++--
 drivers/staging/lustre/lustre/llite/xattr.c         |  7 ++++---
 drivers/staging/lustre/lustre/osc/lproc_osc.c       |  3 ---
 drivers/staging/media/davinci_vpfe/dm365_ipipe_hw.c |  2 +-
 drivers/staging/rdma/ehca/ehca_cq.c                 | 13 +++++++------
 drivers/tty/serial/lpc32xx_hs.c                     |  7 ++++---
 drivers/usb/host/ehci-msm.c                         |  6 +++---
 drivers/video/fbdev/omap/omapfb_main.c              |  5 -----
 fs/cachefiles/bind.c                                |  9 +++------
 fs/cachefiles/daemon.c                              |  6 +++---
 lib/zlib_deflate/deftree.c                          |  2 +-
 mm/memblock.c                                       |  2 +-
 net/openvswitch/conntrack.c                         |  2 +-
 tools/testing/selftests/timers/clocksource-switch.c |  2 +-
 42 files changed, 79 insertions(+), 119 deletions(-)

-- 
1.9.1

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/intel-gfx

[PATCH 08/38] openvswitch: fix handling result of ipv6_skip_exthdr

[Andrzej Hajda]

The function can return negative value.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
---
 net/openvswitch/conntrack.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index 002a755..fde3391 100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -253,7 +253,7 @@ static int ovs_ct_helper(struct sk_buff *skb, u16 proto)
 	const struct nf_conntrack_helper *helper;
 	const struct nf_conn_help *help;
 	enum ip_conntrack_info ctinfo;
-	unsigned int protoff;
+	int protoff;
 	struct nf_conn *ct;
 
 	ct = nf_ct_get(skb, &ctinfo);
-- 
1.9.1

_______________________________________________
dev mailing list
dev@openvswitch.org
http://openvswitch.org/mailman/listinfo/dev

[PATCH 17/38] isdn: hisax: fix frame calculation

[Andrzej Hajda]

Difference of unsigned values is also unsigned so it does not make
sense to check its sign.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
---
 drivers/isdn/hisax/hfc4s8s_l1.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/isdn/hisax/hfc4s8s_l1.c b/drivers/isdn/hisax/hfc4s8s_l1.c
index 0e5d673..9600cd7 100644
--- a/drivers/isdn/hisax/hfc4s8s_l1.c
+++ b/drivers/isdn/hisax/hfc4s8s_l1.c
@@ -646,14 +646,14 @@ rx_d_frame(struct hfc4s8s_l1 *l1p, int ech)
 
 		f1 = Read_hfc8_stable(l1p->hw, A_F1);
 		f2 = Read_hfc8(l1p->hw, A_F2);
-		df = f1 - f2;
-		if ((f1 - f2) < 0)
-			df = f1 - f2 + MAX_F_CNT + 1;
 
+		if (f1 < f2)
+			df = MAX_F_CNT + 1 + f1 - f2;
+		else
+			df = f1 - f2;
 
-		if (!df) {
+		if (!df)
 			return;	/* no complete frame in fifo */
-		}
 
 		z1 = Read_hfc16_stable(l1p->hw, A_Z1);
 		z2 = Read_hfc16(l1p->hw, A_Z2);
-- 
1.9.1

[PATCH 18/38] net/ibm/emac: fix type of phy_mode

[Andrzej Hajda]

phy_mode can be negative.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
---
 drivers/net/ethernet/ibm/emac/core.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ibm/emac/core.h b/drivers/net/ethernet/ibm/emac/core.h
index 28df374..f379e47 100644
--- a/drivers/net/ethernet/ibm/emac/core.h
+++ b/drivers/net/ethernet/ibm/emac/core.h
@@ -181,7 +181,7 @@ struct emac_instance {
 	struct mal_commac		commac;
 
 	/* PHY infos */
-	u32				phy_mode;
+	int				phy_mode;
 	u32				phy_map;
 	u32				phy_address;
 	u32				phy_feat_exc;
-- 
1.9.1

[PATCH 19/38] net: stmmac: fix type of entry variable

[Andrzej Hajda]

Variable can store negative values.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 925f2f8..934143e 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1945,7 +1945,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct stmmac_priv *priv = netdev_priv(dev);
 	unsigned int txsize = priv->dma_tx_size;
-	unsigned int entry;
+	int entry;
 	int i, csum_insertion = 0, is_jumbo = 0;
 	int nfrags = skb_shinfo(skb)->nr_frags;
 	struct dma_desc *desc, *first;
-- 
1.9.1

[PATCH 20/38] net: brcm80211: fix range check

[Andrzej Hajda]

Unsigned minus constant is still unsigned so checking its sign makes no
sense.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
---
 drivers/net/wireless/brcm80211/brcmsmac/main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/brcm80211/brcmsmac/main.c b/drivers/net/wireless/brcm80211/brcmsmac/main.c
index 9728be0..218cbc8 100644
--- a/drivers/net/wireless/brcm80211/brcmsmac/main.c
+++ b/drivers/net/wireless/brcm80211/brcmsmac/main.c
@@ -4585,7 +4585,7 @@ static int brcms_b_attach(struct brcms_c_info *wlc, struct bcma_device *core,
 		wlc_hw->machwcap_backup = wlc_hw->machwcap;
 
 		/* init tx fifo size */
-		WARN_ON((wlc_hw->corerev - XMTFIFOTBL_STARTREV) < 0 ||
+		WARN_ON(wlc_hw->corerev < XMTFIFOTBL_STARTREV ||
 			(wlc_hw->corerev - XMTFIFOTBL_STARTREV) >
 				ARRAY_SIZE(xmtfifo_sz));
 		wlc_hw->xmtfifo_sz =
-- 
1.9.1

[PATCH 21/38] mwifiex: fix comparison expression

[Andrzej Hajda]

To avoid underflows signed variables should be used in expression.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
---
 drivers/net/wireless/mwifiex/11n_rxreorder.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/mwifiex/11n_rxreorder.c b/drivers/net/wireless/mwifiex/11n_rxreorder.c
index 2906cd5..b3970a8 100644
--- a/drivers/net/wireless/mwifiex/11n_rxreorder.c
+++ b/drivers/net/wireless/mwifiex/11n_rxreorder.c
@@ -615,10 +615,10 @@ int mwifiex_11n_rx_reorder_pkt(struct mwifiex_private *priv,
 	    ((end_win > start_win) && ((seq_num > end_win) ||
 				       (seq_num < start_win)))) {
 		end_win = seq_num;
-		if (((seq_num - win_size) + 1) >= 0)
+		if (((end_win - win_size) + 1) >= 0)
 			start_win = (end_win - win_size) + 1;
 		else
-			start_win = (MAX_TID_VALUE - (win_size - seq_num)) + 1;
+			start_win = (MAX_TID_VALUE - (win_size - end_win)) + 1;
 		mwifiex_11n_dispatch_pkt_until_start_win(priv, tbl, start_win);
 	}
 
-- 
1.9.1

[PATCH 22/38] orinoco: fix checking for default value

[Andrzej Hajda]

Thresholds uses -1 to indicate that default value should be used.
Since thresholds are unsigned sign checking makes no sense.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
---
 drivers/net/wireless/orinoco/cfg.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/orinoco/cfg.c b/drivers/net/wireless/orinoco/cfg.c
index a9e94b6..0f6ea31 100644
--- a/drivers/net/wireless/orinoco/cfg.c
+++ b/drivers/net/wireless/orinoco/cfg.c
@@ -220,7 +220,7 @@ static int orinoco_set_wiphy_params(struct wiphy *wiphy, u32 changed)
 	if (changed & WIPHY_PARAM_FRAG_THRESHOLD) {
 		/* Set fragmentation */
 		if (priv->has_mwo) {
-			if (wiphy->frag_threshold < 0)
+			if (wiphy->frag_threshold == -1)
 				frag_value = 0;
 			else {
 				printk(KERN_WARNING "%s: Fixed fragmentation "
@@ -230,7 +230,7 @@ static int orinoco_set_wiphy_params(struct wiphy *wiphy, u32 changed)
 				frag_value = 1;
 			}
 		} else {
-			if (wiphy->frag_threshold < 0)
+			if (wiphy->frag_threshold == -1)
 				frag_value = 2346;
 			else if ((wiphy->frag_threshold < 257) ||
 				 (wiphy->frag_threshold > 2347))
@@ -252,7 +252,7 @@ static int orinoco_set_wiphy_params(struct wiphy *wiphy, u32 changed)
 		 * the upper limit.
 		 */
 
-		if (wiphy->rts_threshold < 0)
+		if (wiphy->rts_threshold == -1)
 			rts_value = 2347;
 		else if (wiphy->rts_threshold > 2347)
 			err = -EINVAL;
-- 
1.9.1

[PATCH 23/38] rndis_wlan: fix checking for default value

[Andrzej Hajda]

Thresholds uses -1 to indicate that default value should be used.
Since thresholds are unsigned sign checking makes no sense.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
---
 drivers/net/wireless/rndis_wlan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/rndis_wlan.c b/drivers/net/wireless/rndis_wlan.c
index 71a825c..a13d1f2 100644
--- a/drivers/net/wireless/rndis_wlan.c
+++ b/drivers/net/wireless/rndis_wlan.c
@@ -1236,7 +1236,7 @@ static int set_rts_threshold(struct usbnet *usbdev, u32 rts_threshold)
 
 	netdev_dbg(usbdev->net, "%s(): %i\n", __func__, rts_threshold);
 
-	if (rts_threshold < 0 || rts_threshold > 2347)
+	if (rts_threshold == -1 || rts_threshold > 2347)
 		rts_threshold = 2347;
 
 	tmp = cpu_to_le32(rts_threshold);
-- 
1.9.1

[PATCH 27/38] usbnet: remove invalid check

[Andrzej Hajda]

skb->len is always non-negative.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
---
 drivers/net/usb/lan78xx.c  | 5 -----
 drivers/net/usb/smsc75xx.c | 5 -----
 drivers/net/usb/smsc95xx.c | 5 -----
 3 files changed, 15 deletions(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index a39518f..e0556dc 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2522,11 +2522,6 @@ static int lan78xx_rx(struct lan78xx_net *dev, struct sk_buff *skb)
 			skb_pull(skb, align_count);
 	}
 
-	if (unlikely(skb->len < 0)) {
-		netdev_warn(dev->net, "invalid rx length<0 %d", skb->len);
-		return 0;
-	}
-
 	return 1;
 }
 
diff --git a/drivers/net/usb/smsc75xx.c b/drivers/net/usb/smsc75xx.c
index d9e7892..30033db 100644
--- a/drivers/net/usb/smsc75xx.c
+++ b/drivers/net/usb/smsc75xx.c
@@ -2185,11 +2185,6 @@ static int smsc75xx_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 			skb_pull(skb, align_count);
 	}
 
-	if (unlikely(skb->len < 0)) {
-		netdev_warn(dev->net, "invalid rx length<0 %d\n", skb->len);
-		return 0;
-	}
-
 	return 1;
 }
 
diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index 26423ad..66b3ab9 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1815,11 +1815,6 @@ static int smsc95xx_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 			skb_pull(skb, align_count);
 	}
 
-	if (unlikely(skb->len < 0)) {
-		netdev_warn(dev->net, "invalid rx length<0 %d\n", skb->len);
-		return 0;
-	}
-
 	return 1;
 }
 
-- 
1.9.1

Re: [PATCH 08/38] openvswitch: fix handling result of ipv6_skip_exthdr

[Pravin Shelar]

On Mon, Sep 21, 2015 at 6:33 AM, Andrzej Hajda <a.hajda@samsung.com> wrote:
> The function can return negative value.
>
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
>
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
>
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
> ---
>  net/openvswitch/conntrack.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
> index 002a755..fde3391 100644
> --- a/net/openvswitch/conntrack.c
> +++ b/net/openvswitch/conntrack.c
> @@ -253,7 +253,7 @@ static int ovs_ct_helper(struct sk_buff *skb, u16 proto)
>         const struct nf_conntrack_helper *helper;
>         const struct nf_conn_help *help;
>         enum ip_conntrack_info ctinfo;
> -       unsigned int protoff;
> +       int protoff;
>         struct nf_conn *ct;
>

A patch is already pushed to the net tree to fix this issue.

Re: [PATCH 00/38] Fixes related to incorrect usage of unsigned types

[Andrzej Hajda]

On 09/21/2015 03:42 PM, David Howells wrote:
> Andrzej Hajda <a.hajda-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org> wrote:
> 
>> Semantic patch finds comparisons of types:
>>     unsigned < 0
>>     unsigned >= 0
>> The former is always false, the latter is always true.
>> Such comparisons are useless, so theoretically they could be
>> safely removed, but their presence quite often indicates bugs.
> 
> Or someone has left them in because they don't matter and there's the
> possibility that the type being tested might be or become signed under some
> circumstances.  If the comparison is useless, I'd expect the compiler to just
> discard it - for such cases your patch is pointless.
> 
> If I have, for example:
> 
> 	unsigned x;
> 
> 	if (x == 0 || x > 27)
> 		give_a_range_error();
> 
> I will write this as:
> 
> 	unsigned x;
> 
> 	if (x <= 0 || x > 27)
> 		give_a_range_error();
> 
> because it that gives a way to handle x being changed to signed at some point
> in the future for no cost.  In which case, your changing the <= to an ==
> "because the < part of the case is useless" is arguably wrong.

This is why I have not checked for such cases - I have skipped checks of type
	unsigned <= 0
exactly for the reasons above.

However I have left two other checks as they seems to me more suspicious - they
are always true or false. But as Dmitry and Andrew pointed out Linus have quite
strong opinion against removing range checks in such cases as he finds it
clearer. I think it applies to patches 29-36. I am not sure about patches 26-28,37.

Regards
Andrzej

> 
> David
> --
> To unsubscribe from this list: send the line "unsubscribe linux-wireless" in
> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/intel-gfx

Re: [PATCH 00/38] Fixes related to incorrect usage of unsigned types

[Jacek Anaszewski]

On 09/22/2015 11:13 AM, Andrzej Hajda wrote:
> On 09/21/2015 03:42 PM, David Howells wrote:
>> Andrzej Hajda <a.hajda-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org> wrote:
>>
>>> Semantic patch finds comparisons of types:
>>>      unsigned < 0
>>>      unsigned >= 0
>>> The former is always false, the latter is always true.
>>> Such comparisons are useless, so theoretically they could be
>>> safely removed, but their presence quite often indicates bugs.
>>
>> Or someone has left them in because they don't matter and there's the
>> possibility that the type being tested might be or become signed under some
>> circumstances.  If the comparison is useless, I'd expect the compiler to just
>> discard it - for such cases your patch is pointless.
>>
>> If I have, for example:
>>
>> 	unsigned x;
>>
>> 	if (x == 0 || x > 27)
>> 		give_a_range_error();
>>
>> I will write this as:
>>
>> 	unsigned x;
>>
>> 	if (x <= 0 || x > 27)
>> 		give_a_range_error();
>>
>> because it that gives a way to handle x being changed to signed at some point
>> in the future for no cost.  In which case, your changing the <= to an ==
>> "because the < part of the case is useless" is arguably wrong.
>
> This is why I have not checked for such cases - I have skipped checks of type
> 	unsigned <= 0
> exactly for the reasons above.
>
> However I have left two other checks as they seems to me more suspicious - they
> are always true or false. But as Dmitry and Andrew pointed out Linus have quite
> strong opinion against removing range checks in such cases as he finds it
> clearer. I think it applies to patches 29-36. I am not sure about patches 26-28,37.

Dropped 30/38 and 31/38 from LED tree then.

-- 
Best Regards,
Jacek Anaszewski

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

RE: [PATCH 21/38] mwifiex: fix comparison expression

[Amitkumar Karwar]

Hi Andrzej,

> From: Andrzej Hajda [mailto:a.hajda@samsung.com]
> Sent: Monday, September 21, 2015 7:04 PM
> To: linux-kernel@vger.kernel.org
> Cc: Andrzej Hajda; Bartlomiej Zolnierkiewicz; Marek Szyprowski;
> Amitkumar Karwar; Nishant Sarmukadam; Kalle Valo; linux-
> wireless@vger.kernel.org; netdev@vger.kernel.org
> Subject: [PATCH 21/38] mwifiex: fix comparison expression
> 
> To avoid underflows signed variables should be used in expression.
> 
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
> 
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
> ---
>  drivers/net/wireless/mwifiex/11n_rxreorder.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/mwifiex/11n_rxreorder.c
> b/drivers/net/wireless/mwifiex/11n_rxreorder.c
> index 2906cd5..b3970a8 100644
> --- a/drivers/net/wireless/mwifiex/11n_rxreorder.c
> +++ b/drivers/net/wireless/mwifiex/11n_rxreorder.c
> @@ -615,10 +615,10 @@ int mwifiex_11n_rx_reorder_pkt(struct
> mwifiex_private *priv,
>  	    ((end_win > start_win) && ((seq_num > end_win) ||
>  				       (seq_num < start_win)))) {
>  		end_win = seq_num;
> -		if (((seq_num - win_size) + 1) >= 0)
> +		if (((end_win - win_size) + 1) >= 0)
>  			start_win = (end_win - win_size) + 1;
>  		else
> -			start_win = (MAX_TID_VALUE - (win_size - seq_num)) +
> 1;
> +			start_win = (MAX_TID_VALUE - (win_size - end_win)) +
> 1;
>  		mwifiex_11n_dispatch_pkt_until_start_win(priv, tbl,
> start_win);
>  	}
> 

Acked-by: Amitkumar Karwar <akarwar@marvell.com>

Regards,
Amitkumar

Re: [PATCH 18/38] net/ibm/emac: fix type of phy_mode

[David Miller]

From: Andrzej Hajda <a.hajda@samsung.com>
Date: Mon, 21 Sep 2015 15:33:50 +0200

> phy_mode can be negative.
> 
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
> 
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

Applied.

Re: [PATCH 27/38] usbnet: remove invalid check

[David Miller]

From: Andrzej Hajda <a.hajda@samsung.com>
Date: Mon, 21 Sep 2015 15:33:59 +0200

> skb->len is always non-negative.
> 
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
> 
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

Applied.

Re: [PATCH 22/38] orinoco: fix checking for default value

[David Miller]

From: Andrzej Hajda <a.hajda@samsung.com>
Date: Mon, 21 Sep 2015 15:33:54 +0200

> Thresholds uses -1 to indicate that default value should be used.
> Since thresholds are unsigned sign checking makes no sense.
> 
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
> 
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

Applied.

Re: [PATCH 21/38] mwifiex: fix comparison expression

[David Miller]

From: Andrzej Hajda <a.hajda@samsung.com>
Date: Mon, 21 Sep 2015 15:33:53 +0200

> To avoid underflows signed variables should be used in expression.
> 
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
> 
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

Applied.

Re: [PATCH 23/38] rndis_wlan: fix checking for default value

[David Miller]

From: Andrzej Hajda <a.hajda@samsung.com>
Date: Mon, 21 Sep 2015 15:33:55 +0200

> Thresholds uses -1 to indicate that default value should be used.
> Since thresholds are unsigned sign checking makes no sense.
> 
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
> 
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

Applied.

Re: [PATCH 19/38] net: stmmac: fix type of entry variable

[David Miller]

From: Andrzej Hajda <a.hajda@samsung.com>
Date: Mon, 21 Sep 2015 15:33:51 +0200

> Variable can store negative values.
> 
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
> 
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

Applied.

Re: [PATCH 17/38] isdn: hisax: fix frame calculation

[David Miller]

From: Andrzej Hajda <a.hajda@samsung.com>
Date: Mon, 21 Sep 2015 15:33:49 +0200

> Difference of unsigned values is also unsigned so it does not make
> sense to check its sign.
> 
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
> 
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

Applied.

Re: [PATCH 20/38] net: brcm80211: fix range check

[David Miller]

From: Andrzej Hajda <a.hajda@samsung.com>
Date: Mon, 21 Sep 2015 15:33:52 +0200

> Unsigned minus constant is still unsigned so checking its sign makes no
> sense.
> 
> The problem has been detected using proposed semantic patch
> scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
> 
> [1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

Applied.