lib: os: spsc_pbuf: Fix free space calculation

nordic-krch · nashif · commit 09b41829a8aa · 2022-08-02T08:13:31.000-04:00
Fixing bug in free space calculation which was assuming 1 byte
padding and not 32 bit word padding. Bug could result in the
data corruption in certain scenario.

Signed-off-by: Krzysztof Chruscinski &lt;krzysztof.chruscinski@nordicsemi.no&gt;
diff --git a/lib/os/spsc_pbuf.c b/lib/os/spsc_pbuf.c
@@ -184,7 +184,7 @@ int spsc_pbuf_alloc(struct spsc_pbuf *pb, uint16_t len, char **buf)
 			}
 		}
 	} else {
-		free_space = rd_idx - wr_idx - 1;
+		free_space = rd_idx - wr_idx - sizeof(uint32_t);
 	}
 
 	len = MIN(len, MAX(free_space - (int32_t)LEN_SZ, 0));

Original file line number	Diff line number	Diff line change
`@@ -184,7 +184,7 @@ int spsc_pbuf_alloc(struct spsc_pbuf pb, uint16_t len, char *buf)`
`184`	`184`	`}`
`185`	`185`	`}`
`186`	`186`	`} else {`
`187`		`- free_space = rd_idx - wr_idx - 1;`
	`187`	`+ free_space = rd_idx - wr_idx - sizeof(uint32_t);`
`188`	`188`	`}`
`189`	`189`
`190`	`190`	`len = MIN(len, MAX(free_space - (int32_t)LEN_SZ, 0));`