[dpdk-dev] [PATCH] eal: fix off-by-one error in hotplug add

[dpdk-dev] [PATCH] eal: fix off-by-one error in hotplug add

[Gaetan Rivet]

snprintf returns the length it would have written had the given length
been enough, *terminating null byte excluded*.

It will however limit the length of its writing to given length minus
one, and always put a terminating null-byte at the end of the string.

This must be taken into account when calculating the total length of the
device declaration string.

Fixes: 3054036f054a ("eal: fix possible crash in hotplug")

Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
---

Charybdis -> Scylla

 lib/librte_eal/common/eal_common_dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/librte_eal/common/eal_common_dev.c b/lib/librte_eal/common/eal_common_dev.c
index fc8a4d2..e251275 100644
--- a/lib/librte_eal/common/eal_common_dev.c
+++ b/lib/librte_eal/common/eal_common_dev.c
@@ -133,7 +133,7 @@ full_dev_name(const char *bus, const char *dev, const char *args)
 	char *name;
 	size_t len;
 
-	len = snprintf(NULL, 0, "%s:%s,%s", bus, dev, args);
+	len = snprintf(NULL, 0, "%s:%s,%s", bus, dev, args) + 1;
 	name = calloc(1, len);
 	if (name == NULL) {
 		RTE_LOG(ERR, EAL, "Could not allocate full device name\n");
-- 
2.1.4

Re: [dpdk-dev] [PATCH] eal: fix off-by-one error in hotplug add

[Thomas Monjalon]

04/08/2017 17:30, Gaetan Rivet:
> snprintf returns the length it would have written had the given length
> been enough, *terminating null byte excluded*.
> 
> It will however limit the length of its writing to given length minus
> one, and always put a terminating null-byte at the end of the string.
> 
> This must be taken into account when calculating the total length of the
> device declaration string.
> 
> Fixes: 3054036f054a ("eal: fix possible crash in hotplug")
> 
> Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
> ---
> 
> Charybdis -> Scylla

Oiseau de mauvais augure :)
The best is the enemy of the good.

Applied, thanks