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Date: Wed, 8 May 2024 10:43:04 +0300
From: Dan Carpenter <dan.carpenter@linaro.org>
To: Sagi Grimberg <sagi@grimberg.me>
Cc: Christoph Hellwig <hch@lst.de>, Chaitanya Kulkarni <kch@nvidia.com>,
	Keith Busch <kbusch@kernel.org>, linux-nvme@lists.infradead.org,
	linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: [PATCH] nvmet: prevent sprintf() overflow in
 nvmet_subsys_nsid_exists()
Message-ID: <25e9c58d-d192-4a91-ad40-4c2ea01fbdf5@moroto.mountain>
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The nsid value is a u32 that comes from nvmet_req_find_ns().  It's
endian data and we're on an error path and both of those raise red
flags.  So let's make this safer.

1) Make the buffer large enough for any u32.
2) Remove the unnecessary initialization.
3) Use snprintf() instead of sprintf() for even more safety.
4) The sprintf() function returns the number of bytes printed, not
   counting the NUL terminator. It is impossible for the return value to
   be <= 0 so delete that.

Fixes: 505363957fad ("nvmet: fix nvme status code when namespace is disabled")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
---
 drivers/nvme/target/configfs.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 89a001101a7f..37cd75ff150e 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -757,10 +757,9 @@ static struct configfs_attribute *nvmet_ns_attrs[] = {
 bool nvmet_subsys_nsid_exists(struct nvmet_subsys *subsys, u32 nsid)
 {
 	struct config_item *ns_item;
-	char name[4] = {};
+	char name[12];
 
-	if (sprintf(name, "%u", nsid) <= 0)
-		return false;
+	snprintf(name, sizeof(name), "%u", nsid);
 	mutex_lock(&subsys->namespaces_group.cg_subsys->su_mutex);
 	ns_item = config_group_find_item(&subsys->namespaces_group, name);
 	mutex_unlock(&subsys->namespaces_group.cg_subsys->su_mutex);
-- 
2.43.0