[PATCH] afs: Fix overwriting of result of DNS query

[PATCH] afs: Fix overwriting of result of DNS query

[David Howells]

In afs_update_cell(), ret is the result of the DNS lookup and the errors
are to be handled by a switch - however, the value gets clobbered in
between by setting it to -ENOMEM in case afs_alloc_vlserver_list() fails.

Fix this by moving the setting of -ENOMEM into the error handling for OOM
failure.  Further, only do it if we don't have an alternative error to
return.

Found by Linux Verification Center (linuxtesting.org) with SVACE.  Based on
a patch from Anastasia Belova[1].

Fixes: d5c32c89b208 ("afs: Fix cell DNS lookup")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Anastasia Belova <abelova@astralinux.ru>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: lvc-project@linuxtesting.org
Link: https://lore.kernel.org/r/20231221085849.1463-1-abelova@astralinux.ru/ [1]

---
 fs/afs/cell.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index 988c2ac7cece..926cb1188eba 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -409,10 +409,12 @@ static int afs_update_cell(struct afs_cell *cell)
 		if (ret == -ENOMEM)
 			goto out_wake;
 
-		ret = -ENOMEM;
 		vllist = afs_alloc_vlserver_list(0);
-		if (!vllist)
+		if (!vllist) {
+			if (ret >= 0)
+				ret = -ENOMEM;
 			goto out_wake;
+		}
 
 		switch (ret) {
 		case -ENODATA:

Re: [PATCH] afs: Fix overwriting of result of DNS query

[Jeffrey E Altman]

[-- Attachment #1.1: Type: text/plain, Size: 1514 bytes --]

On 12/21/2023 9:23 AM, David Howells wrote:
> In afs_update_cell(), ret is the result of the DNS lookup and the errors
> are to be handled by a switch - however, the value gets clobbered in
> between by setting it to -ENOMEM in case afs_alloc_vlserver_list() fails.
>
> Fix this by moving the setting of -ENOMEM into the error handling for OOM
> failure.  Further, only do it if we don't have an alternative error to
> return.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.  Based on
> a patch from Anastasia Belova[1].
>
> Fixes: d5c32c89b208 ("afs: Fix cell DNS lookup")
> Signed-off-by: David Howells<dhowells@redhat.com>
> cc: Anastasia Belova<abelova@astralinux.ru>
> cc: Marc Dionne<marc.dionne@auristor.com>
> cc:linux-afs@lists.infradead.org
> cc:lvc-project@linuxtesting.org
> Link:https://lore.kernel.org/r/20231221085849.1463-1-abelova@astralinux.ru/  [1]
>
> ---
>   fs/afs/cell.c |    6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fs/afs/cell.c b/fs/afs/cell.c
> index 988c2ac7cece..926cb1188eba 100644
> --- a/fs/afs/cell.c
> +++ b/fs/afs/cell.c
> @@ -409,10 +409,12 @@ static int afs_update_cell(struct afs_cell *cell)
>   		if (ret == -ENOMEM)
>   			goto out_wake;
>   
> -		ret = -ENOMEM;
>   		vllist = afs_alloc_vlserver_list(0);
> -		if (!vllist)
> +		if (!vllist) {
> +			if (ret >= 0)
> +				ret = -ENOMEM;
>   			goto out_wake;
> +		}
>   
>   		switch (ret) {
>   		case -ENODATA:
>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>

[-- Attachment #1.2: Type: text/html, Size: 2446 bytes --]

[-- Attachment #2: S/MIME Cryptographic Signature --]
[-- Type: application/pkcs7-signature, Size: 4039 bytes --]

Re: [PATCH] afs: Fix overwriting of result of DNS query

[Jeffrey E Altman]

[-- Attachment #1: Type: text/plain, Size: 1515 bytes --]

On 12/21/2023 9:23 AM, David Howells wrote:
> In afs_update_cell(), ret is the result of the DNS lookup and the errors
> are to be handled by a switch - however, the value gets clobbered in
> between by setting it to -ENOMEM in case afs_alloc_vlserver_list() fails.
>
> Fix this by moving the setting of -ENOMEM into the error handling for OOM
> failure.  Further, only do it if we don't have an alternative error to
> return.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.  Based on
> a patch from Anastasia Belova[1].
>
> Fixes: d5c32c89b208 ("afs: Fix cell DNS lookup")
> Signed-off-by: David Howells<dhowells@redhat.com>
> cc: Anastasia Belova<abelova@astralinux.ru>
> cc: Marc Dionne<marc.dionne@auristor.com>
> cc:linux-afs@lists.infradead.org
> cc:lvc-project@linuxtesting.org
> Link:https://lore.kernel.org/r/20231221085849.1463-1-abelova@astralinux.ru/  [1]
>
> ---
>   fs/afs/cell.c |    6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fs/afs/cell.c b/fs/afs/cell.c
> index 988c2ac7cece..926cb1188eba 100644
> --- a/fs/afs/cell.c
> +++ b/fs/afs/cell.c
> @@ -409,10 +409,12 @@ static int afs_update_cell(struct afs_cell *cell)
>   		if (ret == -ENOMEM)
>   			goto out_wake;
>   
> -		ret = -ENOMEM;
>   		vllist = afs_alloc_vlserver_list(0);
> -		if (!vllist)
> +		if (!vllist) {
> +			if (ret >= 0)
> +				ret = -ENOMEM;
>   			goto out_wake;
> +		}
>   
>   		switch (ret) {
>   		case -ENODATA:
>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>


[-- Attachment #2: S/MIME Cryptographic Signature --]
[-- Type: application/pkcs7-signature, Size: 4039 bytes --]

[PATCH] afs: Fix overwriting of result of DNS query

[David Howells]

Hi Linus,

Could you apply this fix, please?

Thanks,
David
---

In afs_update_cell(), ret is the result of the DNS lookup and the errors
are to be handled by a switch - however, the value gets clobbered in
between by setting it to -ENOMEM in case afs_alloc_vlserver_list() fails.

Fix this by moving the setting of -ENOMEM into the error handling for OOM
failure.  Further, only do it if we don't have an alternative error to
return.

Found by Linux Verification Center (linuxtesting.org) with SVACE.  Based on
a patch from Anastasia Belova[1].

Fixes: d5c32c89b208 ("afs: Fix cell DNS lookup")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
cc: Anastasia Belova <abelova@astralinux.ru>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: lvc-project@linuxtesting.org
Link: https://lore.kernel.org/r/20231221085849.1463-1-abelova@astralinux.ru/ [1]
Link: https://lore.kernel.org/r/1700862.1703168632@warthog.procyon.org.uk/ # v1
---
 fs/afs/cell.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index 988c2ac7cece..926cb1188eba 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -409,10 +409,12 @@ static int afs_update_cell(struct afs_cell *cell)
 		if (ret == -ENOMEM)
 			goto out_wake;
 
-		ret = -ENOMEM;
 		vllist = afs_alloc_vlserver_list(0);
-		if (!vllist)
+		if (!vllist) {
+			if (ret >= 0)
+				ret = -ENOMEM;
 			goto out_wake;
+		}
 
 		switch (ret) {
 		case -ENODATA:

Re: [PATCH] afs: Fix overwriting of result of DNS query

[Linus Torvalds]

On Thu, 21 Dec 2023 at 07:09, David Howells <dhowells@redhat.com> wrote:
>
> Could you apply this fix, please?

Ok, so this is just *annoying*.

Why did you send me this as a patch, and then *twenty minutes* later
you send me an AFS pull request that does *not* include this patch?

WTF?

I've applied this, but I'm really annoyed, because it really feels
like you went out of your way to just generate unnecessary noise and
pointless workflow churn.

It's not even like the pull request contained anything different. The
patch _and_ the pull request were both not just about AFS, but about
DNS issues in AFS.

Get your act together.

                    Linus