[PATCH net] inet: fix inet_fill_ifaddr() flags truncation

[PATCH net] inet: fix inet_fill_ifaddr() flags truncation

[Eric Dumazet]

I missed that (struct ifaddrmsg)->ifa_flags was only 8bits,
while (struct in_ifaddr)->ifa_flags is 32bits.

Use a temporary 32bit variable as I did in set_ifa_lifetime()
and check_lifetime().

Fixes: 3ddc2231c810 ("inet: annotate data-races around ifa->ifa_flags")
Reported-by: Yu Watanabe <watanabe.yu@gmail.com>
Dianosed-by: Yu Watanabe <watanabe.yu@gmail.com>
Closes: https://github.com/systemd/systemd/pull/32666#issuecomment-2103977928
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/devinet.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 7a437f0d41905e6acfdc35743afba3a7abfd0dd5..7e45c34c8340a6d2cf96b4485cd4249fd4da7009 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1683,6 +1683,7 @@ static int inet_fill_ifaddr(struct sk_buff *skb, const struct in_ifaddr *ifa,
 	struct nlmsghdr  *nlh;
 	unsigned long tstamp;
 	u32 preferred, valid;
+	u32 flags;
 
 	nlh = nlmsg_put(skb, args->portid, args->seq, args->event, sizeof(*ifm),
 			args->flags);
@@ -1692,7 +1693,13 @@ static int inet_fill_ifaddr(struct sk_buff *skb, const struct in_ifaddr *ifa,
 	ifm = nlmsg_data(nlh);
 	ifm->ifa_family = AF_INET;
 	ifm->ifa_prefixlen = ifa->ifa_prefixlen;
-	ifm->ifa_flags = READ_ONCE(ifa->ifa_flags);
+
+	flags = READ_ONCE(ifa->ifa_flags);
+	/* Warning : ifm->ifa_flags is an __u8, it holds only 8 bits.
+	 * The 32bit value is given in IFA_FLAGS attribute.
+	 */
+	ifm->ifa_flags = (__u8)flags;
+
 	ifm->ifa_scope = ifa->ifa_scope;
 	ifm->ifa_index = ifa->ifa_dev->dev->ifindex;
 
@@ -1701,7 +1708,7 @@ static int inet_fill_ifaddr(struct sk_buff *skb, const struct in_ifaddr *ifa,
 		goto nla_put_failure;
 
 	tstamp = READ_ONCE(ifa->ifa_tstamp);
-	if (!(ifm->ifa_flags & IFA_F_PERMANENT)) {
+	if (!(flags & IFA_F_PERMANENT)) {
 		preferred = READ_ONCE(ifa->ifa_preferred_lft);
 		valid = READ_ONCE(ifa->ifa_valid_lft);
 		if (preferred != INFINITY_LIFE_TIME) {
@@ -1732,7 +1739,7 @@ static int inet_fill_ifaddr(struct sk_buff *skb, const struct in_ifaddr *ifa,
 	     nla_put_string(skb, IFA_LABEL, ifa->ifa_label)) ||
 	    (ifa->ifa_proto &&
 	     nla_put_u8(skb, IFA_PROTO, ifa->ifa_proto)) ||
-	    nla_put_u32(skb, IFA_FLAGS, ifm->ifa_flags) ||
+	    nla_put_u32(skb, IFA_FLAGS, flags) ||
 	    (ifa->ifa_rt_priority &&
 	     nla_put_u32(skb, IFA_RT_PRIORITY, ifa->ifa_rt_priority)) ||
 	    put_cacheinfo(skb, READ_ONCE(ifa->ifa_cstamp), tstamp,
-- 
2.45.0.118.g7fe29c98d7-goog

Re: [PATCH net] inet: fix inet_fill_ifaddr() flags truncation

[Larysa Zaremba]

On Fri, May 10, 2024 at 07:29:32AM +0000, Eric Dumazet wrote:
> I missed that (struct ifaddrmsg)->ifa_flags was only 8bits,
> while (struct in_ifaddr)->ifa_flags is 32bits.
> 
> Use a temporary 32bit variable as I did in set_ifa_lifetime()
> and check_lifetime().
> 
> Fixes: 3ddc2231c810 ("inet: annotate data-races around ifa->ifa_flags")
> Reported-by: Yu Watanabe <watanabe.yu@gmail.com>
> Dianosed-by: Yu Watanabe <watanabe.yu@gmail.com>
> Closes: https://github.com/systemd/systemd/pull/32666#issuecomment-2103977928

Reviewed-by: Larysa Zaremba <larysa.zaremba@intel.com>

> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>  net/ipv4/devinet.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index 7a437f0d41905e6acfdc35743afba3a7abfd0dd5..7e45c34c8340a6d2cf96b4485cd4249fd4da7009 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -1683,6 +1683,7 @@ static int inet_fill_ifaddr(struct sk_buff *skb, const struct in_ifaddr *ifa,
>  	struct nlmsghdr  *nlh;
>  	unsigned long tstamp;
>  	u32 preferred, valid;
> +	u32 flags;
>  
>  	nlh = nlmsg_put(skb, args->portid, args->seq, args->event, sizeof(*ifm),
>  			args->flags);
> @@ -1692,7 +1693,13 @@ static int inet_fill_ifaddr(struct sk_buff *skb, const struct in_ifaddr *ifa,
>  	ifm = nlmsg_data(nlh);
>  	ifm->ifa_family = AF_INET;
>  	ifm->ifa_prefixlen = ifa->ifa_prefixlen;
> -	ifm->ifa_flags = READ_ONCE(ifa->ifa_flags);
> +
> +	flags = READ_ONCE(ifa->ifa_flags);
> +	/* Warning : ifm->ifa_flags is an __u8, it holds only 8 bits.
> +	 * The 32bit value is given in IFA_FLAGS attribute.
> +	 */
> +	ifm->ifa_flags = (__u8)flags;
> +
>  	ifm->ifa_scope = ifa->ifa_scope;
>  	ifm->ifa_index = ifa->ifa_dev->dev->ifindex;
>  
> @@ -1701,7 +1708,7 @@ static int inet_fill_ifaddr(struct sk_buff *skb, const struct in_ifaddr *ifa,
>  		goto nla_put_failure;
>  
>  	tstamp = READ_ONCE(ifa->ifa_tstamp);
> -	if (!(ifm->ifa_flags & IFA_F_PERMANENT)) {
> +	if (!(flags & IFA_F_PERMANENT)) {
>  		preferred = READ_ONCE(ifa->ifa_preferred_lft);
>  		valid = READ_ONCE(ifa->ifa_valid_lft);
>  		if (preferred != INFINITY_LIFE_TIME) {
> @@ -1732,7 +1739,7 @@ static int inet_fill_ifaddr(struct sk_buff *skb, const struct in_ifaddr *ifa,
>  	     nla_put_string(skb, IFA_LABEL, ifa->ifa_label)) ||
>  	    (ifa->ifa_proto &&
>  	     nla_put_u8(skb, IFA_PROTO, ifa->ifa_proto)) ||
> -	    nla_put_u32(skb, IFA_FLAGS, ifm->ifa_flags) ||
> +	    nla_put_u32(skb, IFA_FLAGS, flags) ||
>  	    (ifa->ifa_rt_priority &&
>  	     nla_put_u32(skb, IFA_RT_PRIORITY, ifa->ifa_rt_priority)) ||
>  	    put_cacheinfo(skb, READ_ONCE(ifa->ifa_cstamp), tstamp,
> -- 
> 2.45.0.118.g7fe29c98d7-goog
> 
> 

Re: [PATCH net] inet: fix inet_fill_ifaddr() flags truncation

[David Ahern]

On 5/10/24 1:29 AM, Eric Dumazet wrote:
> I missed that (struct ifaddrmsg)->ifa_flags was only 8bits,
> while (struct in_ifaddr)->ifa_flags is 32bits.
> 
> Use a temporary 32bit variable as I did in set_ifa_lifetime()
> and check_lifetime().
> 
> Fixes: 3ddc2231c810 ("inet: annotate data-races around ifa->ifa_flags")
> Reported-by: Yu Watanabe <watanabe.yu@gmail.com>
> Dianosed-by: Yu Watanabe <watanabe.yu@gmail.com>
> Closes: https://github.com/systemd/systemd/pull/32666#issuecomment-2103977928
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>  net/ipv4/devinet.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>

Re: [PATCH net] inet: fix inet_fill_ifaddr() flags truncation

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri, 10 May 2024 07:29:32 +0000 you wrote:
> I missed that (struct ifaddrmsg)->ifa_flags was only 8bits,
> while (struct in_ifaddr)->ifa_flags is 32bits.
> 
> Use a temporary 32bit variable as I did in set_ifa_lifetime()
> and check_lifetime().
> 
> Fixes: 3ddc2231c810 ("inet: annotate data-races around ifa->ifa_flags")
> Reported-by: Yu Watanabe <watanabe.yu@gmail.com>
> Dianosed-by: Yu Watanabe <watanabe.yu@gmail.com>
> Closes: https://github.com/systemd/systemd/pull/32666#issuecomment-2103977928
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> 
> [...]

Here is the summary with links:
  - [net] inet: fix inet_fill_ifaddr() flags truncation
    https://git.kernel.org/netdev/net/c/1af7f88af269

You are awesome, thank you!
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