[PATCH net-next] net: dns_resolver: allow shorter names in dns_query()

[PATCH net-next] net: dns_resolver: allow shorter names in dns_query()

[Paulo Alcantara]

Customer reported a problem with mounting CIFS shares where the server
hostname was 2 chars long.  Turned out that the CIFS client wasn't
able to resolve NetBIOS names shorter than 3 chars.

Fix this by allowing a minimum of one character per hostname in
dns_query().

Reproducer with samba server:

  # 'ab' and 'srv' hotnames resolve to same ip address
  $ ssh srv ln -s 'msdfs:\\ab\\share' /home/shares/dfs/link1
  $ mount.cifs //srv/dfs/link1 /mnt -o ... [EINVAL]

Reported-by: Pierguido Lambri <plambri@redhat.com>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
---
 net/dns_resolver/dns_query.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/dns_resolver/dns_query.c b/net/dns_resolver/dns_query.c
index 14bee83cbe22..b8fb9a1245bf 100644
--- a/net/dns_resolver/dns_query.c
+++ b/net/dns_resolver/dns_query.c
@@ -72,7 +72,7 @@ int dns_query(struct net *net,
 	kenter("%s,%*.*s,%zu,%s",
 	       type, (int)namelen, (int)namelen, name, namelen, options);
 
-	if (!name || namelen < 3 || namelen > 255)
+	if (!name || namelen < 1 || namelen > 255)
 		return -EINVAL;
 	if (type && *type == '\0')
 		return -EINVAL;

Re: [PATCH net-next] net: dns_resolver: allow shorter names in dns_query()

[David Howells]

Paulo Alcantara <pc@manguebit.org> wrote:

> Customer reported a problem with mounting CIFS shares where the server
> hostname was 2 chars long.  Turned out that the CIFS client wasn't
> able to resolve NetBIOS names shorter than 3 chars.
> 
> Fix this by allowing a minimum of one character per hostname in
> dns_query().
> 
> Reproducer with samba server:
> 
>   # 'ab' and 'srv' hotnames resolve to same ip address
>   $ ssh srv ln -s 'msdfs:\\ab\\share' /home/shares/dfs/link1
>   $ mount.cifs //srv/dfs/link1 /mnt -o ... [EINVAL]
> 
> Reported-by: Pierguido Lambri <plambri@redhat.com>
> Signed-off-by: Paulo Alcantara <pc@manguebit.org>

Acked-by: David Howells <dhowells@redhat.com>

Re: [PATCH net-next] net: dns_resolver: allow shorter names in dns_query()

[Frank Sorenson]

On 7/22/26 4:28 PM, Paulo Alcantara wrote:
> Customer reported a problem with mounting CIFS shares where the server
> hostname was 2 chars long.  Turned out that the CIFS client wasn't
> able to resolve NetBIOS names shorter than 3 chars.
>
> Fix this by allowing a minimum of one character per hostname in
> dns_query().
>
> Reproducer with samba server:
>
>    # 'ab' and 'srv' hotnames resolve to same ip address
>    $ ssh srv ln -s 'msdfs:\\ab\\share' /home/shares/dfs/link1
>    $ mount.cifs //srv/dfs/link1 /mnt -o ... [EINVAL]
>
> Reported-by: Pierguido Lambri <plambri@redhat.com>
> Signed-off-by: Paulo Alcantara <pc@manguebit.org>
>   		return -EINVAL;

Acked-by: Frank Sorenson <sorenson@redhat.com>

Re: [PATCH net-next] net: dns_resolver: allow shorter names in dns_query()

[patchwork-bot+netdevbpf]

Hello:

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

On Wed, 22 Jul 2026 18:28:37 -0300 you wrote:
> Customer reported a problem with mounting CIFS shares where the server
> hostname was 2 chars long.  Turned out that the CIFS client wasn't
> able to resolve NetBIOS names shorter than 3 chars.
> 
> Fix this by allowing a minimum of one character per hostname in
> dns_query().
> 
> [...]

Here is the summary with links:
  - [net-next] net: dns_resolver: allow shorter names in dns_query()
    https://git.kernel.org/netdev/net-next/c/a50eba1e778a

You are awesome, thank you!
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