* Re: FAILED: patch "[PATCH] smb: smbdirect: fix buffer length underflow in RDMA transfers" failed to apply to 6.12-stable tree
2026-11-04 18:29 FAILED: patch "[PATCH] smb: smbdirect: fix buffer length underflow in RDMA transfers" failed to apply to 6.12-stable tree gregkh
@ 2026-11-05 8:09 ` Stefan Metzmacher
2026-11-06 16:35 ` Sasha Levin
2026-11-05 17:14 ` [PATCH 6.12.y] smb: smbdirect: fix buffer length underflow in RDMA transfers Sasha Levin
1 sibling, 1 reply; 4+ messages in thread
From: Stefan Metzmacher @ 2026-11-05 8:09 UTC (permalink / raw)
To: gregkh, linkinjeon; +Cc: stable
[-- Attachment #1: Type: text/plain, Size: 2801 bytes --]
Am 04.11.26 um 19:29 schrieb gregkh@linuxfoundation.org:
>
> The patch below does not apply to the 6.12-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
>
> To reproduce the conflict and resubmit, you may use the following commands:
>
> git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
> git checkout FETCH_HEAD
> git cherry-pick -x 7193241a49c958782ba4b8df06da3734d1e317d2
> # <resolve conflicts, build, test, etc.>
> git commit -s
> git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026110437-bully-enviable-15b3@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'
>
> Possible dependencies:
>
>
>
> thanks,
>
> greg k-h
>
> ------------------ original commit in Linus's tree ------------------
>
> From 7193241a49c958782ba4b8df06da3734d1e317d2 Mon Sep 17 00:00:00 2001
> From: Stefan Metzmacher <metze@samba.org>
> Date: Fri, 23 Oct 2026 19:26:09 +0900
> Subject: [PATCH] smb: smbdirect: fix buffer length underflow in RDMA transfers
>
> When a remote buffer descriptor is larger than the remaining local
> buffer, smbdirect_connection_rdma_xmit() clamps its length and sets
> buf_len to zero. The common accounting code then subtracts the clamped
> length from buf_len, causing it to underflow. If another descriptor
> follows, the loop processes it with a wrapped remaining length and
> includes memory beyond the local buffer in the RDMA transfer.
>
> A client can trigger an out-of-bounds kernel write with an SMB WRITE
> request, or an out-of-bounds kernel read with an SMB READ request, by
> supplying multiple RDMA buffer descriptors with an oversized descriptor
> before the last one.
>
> Remove the premature assignment to buf_len. Subtracting the clamped length
> already consumes the remaining buffer, so the next iteration stops and
> only descriptors within the local buffer are used to build work requests.
>
> Fixes: e628bf939aaf ("ksmbd: reduce descriptor size if remaining bytes is less than request size")
> Cc: stable@vger.kernel.org
> Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-33549
> Signed-off-by: Stefan Metzmacher <metze@samba.org>
> Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
>
> diff --git a/fs/smb/smbdirect/rw.c b/fs/smb/smbdirect/rw.c
> index 6fe38042cfb9..cb142c3c50b2 100644
> --- a/fs/smb/smbdirect/rw.c
> +++ b/fs/smb/smbdirect/rw.c
> @@ -143,7 +143,6 @@ int smbdirect_connection_rdma_xmit(struct smbdirect_socket *sc,
> if (desc_buf_len > buf_len) {
> desc_buf_len = buf_len;
> desc[i].length = cpu_to_le32(desc_buf_len);
> - buf_len = 0;
> }
>
> credits_needed += smbdirect_connection_calc_rw_credits(sc,
[-- Attachment #2: backport-6.12-smbdirect-rdma-xmit-underflow.txt --]
[-- Type: text/plain, Size: 2134 bytes --]
From 00a805d71893ca99f7d85872346d1ab689aa602f Mon Sep 17 00:00:00 2001
From: Stefan Metzmacher <metze@samba.org>
Date: Fri, 23 Oct 2026 19:26:09 +0900
Subject: [PATCH 6.12.y] smb: smbdirect: fix buffer length underflow in RDMA
transfers
[ Upstream commit 7193241a49c958782ba4b8df06da3734d1e317d2 ]
When a remote buffer descriptor is larger than the remaining local
buffer, smbdirect_connection_rdma_xmit() clamps its length and sets
buf_len to zero. The common accounting code then subtracts the clamped
length from buf_len, causing it to underflow. If another descriptor
follows, the loop processes it with a wrapped remaining length and
includes memory beyond the local buffer in the RDMA transfer.
A client can trigger an out-of-bounds kernel write with an SMB WRITE
request, or an out-of-bounds kernel read with an SMB READ request, by
supplying multiple RDMA buffer descriptors with an oversized descriptor
before the last one.
Remove the premature assignment to buf_len. Subtracting the clamped length
already consumes the remaining buffer, so the next iteration stops and
only descriptors within the local buffer are used to build work requests.
Fixes: e628bf939aaf ("ksmbd: reduce descriptor size if remaining bytes is less than request size")
Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-33549
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
[ metze: in 6.12 the code is smb_direct_rdma_xmit() in
fs/smb/server/transport_rdma.c ]
Assisted-by: Claude:claude-opus-5-5
---
fs/smb/server/transport_rdma.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/fs/smb/server/transport_rdma.c b/fs/smb/server/transport_rdma.c
index 585617595727..be26c2e569e5 100644
--- a/fs/smb/server/transport_rdma.c
+++ b/fs/smb/server/transport_rdma.c
@@ -1388,7 +1388,6 @@ static int smb_direct_rdma_xmit(struct smb_direct_transport *t,
if (desc_buf_len > buf_len) {
desc_buf_len = buf_len;
desc[i].length = cpu_to_le32(desc_buf_len);
- buf_len = 0;
}
credits_needed += calc_rw_credits(t, desc_buf, desc_buf_len);
--
2.53.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH 6.12.y] smb: smbdirect: fix buffer length underflow in RDMA transfers
2026-11-04 18:29 FAILED: patch "[PATCH] smb: smbdirect: fix buffer length underflow in RDMA transfers" failed to apply to 6.12-stable tree gregkh
2026-11-05 8:09 ` Stefan Metzmacher
@ 2026-11-05 17:14 ` Sasha Levin
1 sibling, 0 replies; 4+ messages in thread
From: Sasha Levin @ 2026-11-05 17:14 UTC (permalink / raw)
To: stable; +Cc: Stefan Metzmacher, zdi-disclosures, Namjae Jeon, Sasha Levin
From: Stefan Metzmacher <metze@samba.org>
[ Upstream commit 7193241a49c958782ba4b8df06da3734d1e317d2 ]
When a remote buffer descriptor is larger than the remaining local
buffer, smbdirect_connection_rdma_xmit() clamps its length and sets
buf_len to zero. The common accounting code then subtracts the clamped
length from buf_len, causing it to underflow. If another descriptor
follows, the loop processes it with a wrapped remaining length and
includes memory beyond the local buffer in the RDMA transfer.
A client can trigger an out-of-bounds kernel write with an SMB WRITE
request, or an out-of-bounds kernel read with an SMB READ request, by
supplying multiple RDMA buffer descriptors with an oversized descriptor
before the last one.
Remove the premature assignment to buf_len. Subtracting the clamped length
already consumes the remaining buffer, so the next iteration stops and
only descriptors within the local buffer are used to build work requests.
Fixes: e628bf939aaf ("ksmbd: reduce descriptor size if remaining bytes is less than request size")
Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-33549
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
[ sashal: Retargeted the change from smbdirect_connection_rdma_xmit() to the equivalent smb_direct_rdma_xmit() implementation. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/smb/server/transport_rdma.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/fs/smb/server/transport_rdma.c b/fs/smb/server/transport_rdma.c
index 585617595727b..be26c2e569e57 100644
--- a/fs/smb/server/transport_rdma.c
+++ b/fs/smb/server/transport_rdma.c
@@ -1388,7 +1388,6 @@ static int smb_direct_rdma_xmit(struct smb_direct_transport *t,
if (desc_buf_len > buf_len) {
desc_buf_len = buf_len;
desc[i].length = cpu_to_le32(desc_buf_len);
- buf_len = 0;
}
credits_needed += calc_rw_credits(t, desc_buf, desc_buf_len);
--
2.53.0
^ permalink raw reply related [flat|nested] 4+ messages in thread