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DVB: negative internal->sub_range won't get noticed

PATCH In review Roel Kluin 2 participants 2 messages Jan 18, 2009 – Jan 27, 2009 Media (V4L/DVB)

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Roel Kluin

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#0 lore raw

PATCH 1/1 DVB: negative internal->sub_range won't get noticed

internal->sub_range is unsigned, a negative won't get noticed.

Signed-off-by Roel Kluin <[email protected]>

---

drivers/media/dvb/frontends/stb0899_algo.c +5 -4
index 83dc7e1..2ea32da 100644
@@ -464,13 +464,14 @@ static void next_sub_range(struct stb0899_state *state)
 
 	if (internal->sub_dir > 0) {
 		old_sub_range = internal->sub_range;
-		internal->sub_range = MIN((internal->srch_range / 2) -
+		if (internal->tuner_offst + internal->sub_range / 2 >=
+				internal->srch_range / 2)
+			internal->sub_range = 0;
+		else
+			internal->sub_range = MIN((internal->srch_range / 2) -
 					  (internal->tuner_offst + internal->sub_range / 2),
 					   internal->sub_range);
 
-		if (internal->sub_range < 0)
-			internal->sub_range = 0;
-
 		internal->tuner_offst += (old_sub_range + internal->sub_range) / 2;
 	}
#1 lore raw
Quoted 16 lines · On Mon, 19 Jan 2009 00:35:47 +0100 Roel Kluin <[email protected]> wrote:

internal->sub_range is unsigned, a negative won't get noticed.

Signed-off-by Roel Kluin <[email protected]>

---

drivers/media/dvb/frontends/stb0899_algo.c +3 -1
index 83dc7e1..2ea32da 100644
@@ -464,13 +464,14 @@ static void next_sub_range(struct stb0899_state *state)
 
 	if (internal->sub_dir > 0) {
 		old_sub_range = internal->sub_range;
-		internal->sub_range = MIN((internal->srch_range / 2) -
+		if (internal->tuner_offst + internal->sub_range / 2 >=
+				internal->srch_range / 2)
+			internal->sub_range = 0;

drivers/media/dvb/frontends/stb0899_algo.c static void next_sub_range(struct stb0899_state *state) · line 476

Quoted 10 lines
drivers/media/dvb/frontends/stb0899_algo.c +2 -3
+		else
+			internal->sub_range = MIN((internal->srch_range / 2) -
 					  (internal->tuner_offst + internal->sub_range / 2),
 					   internal->sub_range);
 
-		if (internal->sub_range < 0)
-			internal->sub_range = 0;
-
 		internal->tuner_offst += (old_sub_range + internal->sub_range) / 2;
 	}

I hope someone understands that function :(

Do we actually need that test at all? Perhaps it has never triggered? Perhaps values in the 0x80000000 - 0xffffffff are actually OK?

This driver has managed to get itself a secret private version of the min(), max() and abs() macros. They're buggy - they reference their argument multiple times. The driver should be converted to use the kernel.h versions.

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