[PATCH net v2] net: mvneta: Fix an out of bounds check

In an earlier commit, I added a bounds check to prevent an out of bounds
read and a WARN().  On further discussion and consideration that check
was probably too aggressive.  Instead of returning -EINVAL, a better fix
would be to just prevent the out of bounds read but continue the process.

Background: The value of "pp->rxq_def" is a number between 0-7 by default,
or even higher depending on the value of "rxq_number", which is a module
parameter. If the value is more than the number of available CPUs then
it will trigger the WARN() in cpu_max_bits_warn().

Fixes: e8b4fc13900b ("net: mvneta: Prevent out of bounds read in mvneta_config_rss()")
Signed-off-by: Dan Carpenter <redacted>
---
v2: fix the subject to say net instead of net-next.

 drivers/net/ethernet/marvell/mvneta.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 66b7f27c9a48..5aefaaff0871 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c

@@ -4271,7 +4271,7 @@ static void mvneta_percpu_elect(struct mvneta_port *pp)
 	/* Use the cpu associated to the rxq when it is online, in all
 	 * the other cases, use the cpu 0 which can't be offline.
 	 */
-	if (cpu_online(pp->rxq_def))
+	if (pp->rxq_def < nr_cpu_ids && cpu_online(pp->rxq_def))
 		elected_cpu = pp->rxq_def;
 
 	max_cpu = num_present_cpus();

@@ -4927,9 +4927,6 @@ static int  mvneta_config_rss(struct mvneta_port *pp)
 		napi_disable(&pp->napi);
 	}
 
-	if (pp->indir[0] >= nr_cpu_ids)
-		return -EINVAL;
-
 	pp->rxq_def = pp->indir[0];
 
 	/* Update unicast mapping */

-- 
2.35.1

On Wed, Dec 07, 2022 at 10:06:31AM +0300, Dan Carpenter wrote:

In an earlier commit, I added a bounds check to prevent an out of bounds
read and a WARN().  On further discussion and consideration that check
was probably too aggressive.  Instead of returning -EINVAL, a better fix
would be to just prevent the out of bounds read but continue the process.

Background: The value of "pp->rxq_def" is a number between 0-7 by default,
or even higher depending on the value of "rxq_number", which is a module
parameter. If the value is more than the number of available CPUs then
it will trigger the WARN() in cpu_max_bits_warn().

Fixes: e8b4fc13900b ("net: mvneta: Prevent out of bounds read in mvneta_config_rss()")
Signed-off-by: Dan Carpenter <redacted>
---
v2: fix the subject to say net instead of net-next.

 drivers/net/ethernet/marvell/mvneta.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

Thanks for the followup,
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski [off-list ref]:

On Wed, 7 Dec 2022 10:06:31 +0300 you wrote:

In an earlier commit, I added a bounds check to prevent an out of bounds
read and a WARN().  On further discussion and consideration that check
was probably too aggressive.  Instead of returning -EINVAL, a better fix
would be to just prevent the out of bounds read but continue the process.

Background: The value of "pp->rxq_def" is a number between 0-7 by default,
or even higher depending on the value of "rxq_number", which is a module
parameter. If the value is more than the number of available CPUs then
it will trigger the WARN() in cpu_max_bits_warn().

[...]

Here is the summary with links:
  - [net,v2] net: mvneta: Fix an out of bounds check
    https://git.kernel.org/netdev/net/c/cdd97383e19d

You are awesome, thank you!
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