Function mlxfw_mfa2_tlv_multi_get() returns NULL if 'tlv' in
question does not pass checks in mlxfw_mfa2_tlv_payload_get(). This
behaviour may lead to NULL pointer dereference in 'multi->total_len'.
Fix this issue by testing mlxfw_mfa2_tlv_multi_get()'s return value
against NULL.

Found by Linux Verification Center (linuxtesting.org) with static
analysis tool SVACE.

Fixes: 410ed13cae39 ("Add the mlxfw module for Mellanox firmware flash process")
Co-developed-by: Natalia Petrova <n.petrova@fintech.ru>
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
---
 drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2_tlv_multi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2_tlv_multi.c b/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2_tlv_multi.c
index 017d68f1e123..972c571b4158 100644
--- a/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2_tlv_multi.c
+++ b/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2_tlv_multi.c
@@ -31,6 +31,8 @@ mlxfw_mfa2_tlv_next(const struct mlxfw_mfa2_file *mfa2_file,
 
 	if (tlv->type == MLXFW_MFA2_TLV_MULTI_PART) {
 		multi = mlxfw_mfa2_tlv_multi_get(mfa2_file, tlv);
+		if (!multi)
+			return NULL;
 		tlv_len = NLA_ALIGN(tlv_len + be16_to_cpu(multi->total_len));
 	}

Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Mon, 17 Apr 2023 05:07:18 -0700 you wrote:
> Function mlxfw_mfa2_tlv_multi_get() returns NULL if 'tlv' in
> question does not pass checks in mlxfw_mfa2_tlv_payload_get(). This
> behaviour may lead to NULL pointer dereference in 'multi->total_len'.
> Fix this issue by testing mlxfw_mfa2_tlv_multi_get()'s return value
> against NULL.
> 
> Found by Linux Verification Center (linuxtesting.org) with static
> analysis tool SVACE.
> 
> [...]

Here is the summary with links:
  - [net] mlxfw: fix null-ptr-deref in mlxfw_mfa2_tlv_next()
    https://git.kernel.org/netdev/net/c/c0e73276f0fc

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
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On Mon, Apr 17, 2023 at 05:07:18AM -0700, Nikita Zhandarovich wrote:
> Function mlxfw_mfa2_tlv_multi_get() returns NULL if 'tlv' in
> question does not pass checks in mlxfw_mfa2_tlv_payload_get(). This
> behaviour may lead to NULL pointer dereference in 'multi->total_len'.
> Fix this issue by testing mlxfw_mfa2_tlv_multi_get()'s return value
> against NULL.
> 
> Found by Linux Verification Center (linuxtesting.org) with static
> analysis tool SVACE.
> 
> Fixes: 410ed13cae39 ("Add the mlxfw module for Mellanox firmware flash process")
> Co-developed-by: Natalia Petrova <n.petrova@fintech.ru>
> Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>

Reviewed-by: Ido Schimmel <idosch@nvidia.com>