On Mon, 2023-03-27 at 13:14 +0000, Chuck Lever III wrote:

quoted

On Mar 27, 2023, at 6:21 AM, Jeff Layton [off-list ref] wrote:

For ops with "trivial" replies, nfsd4_encode_operation will shortcut
most of the encoding work and skip to just marshalling up the status.
One of the things it skips is calling op_release. This could cause a
memory leak in the layoutget codepath if there is an error at an
inopportune time.

Have the compound processing engine always call op_release, even when
op_func sets an error in op->status. With this change, we also need
nfsd4_block_get_device_info_scsi to set the gd_device pointer to NULL
on error to avoid a double free.

Reported-by: Zhi Li <redacted>
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2181403
Signed-off-by: Jeff Layton <jlayton@kernel.org>

Thanks, Jeff.

May I add: Fixes: 34b1744c91cc ("nfsd4: define ->op_release for
compound ops") ?

Sure. It does look like the leaks stretch back at least that far.
 

quoted

---
fs/nfsd/blocklayout.c |  1 +
fs/nfsd/nfs4xdr.c     | 13 +++++++------
2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/nfsd/blocklayout.c b/fs/nfsd/blocklayout.c
index 04697f8dc37d..01d7fd108cf3 100644
--- a/fs/nfsd/blocklayout.c
+++ b/fs/nfsd/blocklayout.c

@@ -297,6 +297,7 @@ nfsd4_block_get_device_info_scsi(struct super_block *sb,

out_free_dev:
	kfree(dev);
+	gdp->gd_device = NULL;
	return ret;
}

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index e12e5a4ad502..6b675fbdabd0 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c

@@ -5402,7 +5402,7 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)

	p = xdr_reserve_space(xdr, 8);
	if (!p) {
		WARN_ON_ONCE(1);
-		return;
+		goto release;
	}
	*p++ = cpu_to_be32(op->opnum);
	post_err_offset = xdr->buf->len;

@@ -5418,8 +5418,6 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)

	op->status = encoder(resp, op->status, &op->u);
	if (op->status)
		trace_nfsd_compound_encode_err(rqstp, op->opnum, op->status);
-	if (opdesc && opdesc->op_release)
-		opdesc->op_release(&op->u);
	xdr_commit_encode(xdr);

	/* nfsd4_check_resp_size guarantees enough room for error status */

@@ -5460,11 +5458,14 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op)

	}
status:
	*p = op->status;
+release:
+	if (opdesc && opdesc->op_release)
+		opdesc->op_release(&op->u);
}

-/* 
- * Encode the reply stored in the stateowner reply cache 
- * 
+/*
+ * Encode the reply stored in the stateowner reply cache
+ *
 * XDR note: do not encode rp->rp_buflen: the buffer contains the
 * previously sent already encoded operation.
 */
-- 
2.39.2

--
Chuck Lever

-- 
Jeff Layton [off-list ref]