Description
In the Linux kernel, the following vulnerability has been resolved:
xprtrdma: Decouple req recycling from RPC completion
rl_kref formerly served two distinct lifetimes through a single
refcount: it gated when a Reply could wake its RPC task, and it
gated when an rpcrdma_req could return to its free pool. The
marshal path took the Send-side reference only when SGEs needed
DMA-unmap (sc_unmap_count > 0), which made a Send carrying only
pre-registered buffers an exception: the Reply handler dropped
rl_kref from 1 to 0 and freed the req while the HCA might still
be DMA-reading from its send buffer.
Give rl_kref a narrower job. The RPC layer takes one reference
when slot allocation hands a req out. rpcrdma_prepare_send_sges()
takes a Send-side reference unconditionally after WR preparation
succeeds. xprt_rdma_free_slot() and xprt_rdma_bc_free_rqst() drop
the RPC-layer reference; rpcrdma_sendctx_unmap() drops the
Send-side reference. The req returns to its free pool only after
both owners have signed off.
The existing kref_init(&req->rl_kref) call in
rpcrdma_prepare_send_sges() is removed. Initialization moves to
the slot-allocation paths (xprt_rdma_alloc_slot and
rpcrdma_bc_rqst_get), and the release callback re-arms rl_kref
before the req returns to a free pool. A re-init in the marshal
path would discard the RPC-layer reference that already exists
on entry.
Three invariants follow:
- Any rpcrdma_req held by an rpc_rqst has rl_kref >= 1.
xprt_rdma_alloc_slot(), rpcrdma_bc_rqst_get(), and the
backlog-wake branch in xprt_rdma_alloc_slot() each kref_init
rl_kref before publishing the req. Without this invariant,
an RPC task that aborts between slot allocation and marshal
(gss_refresh failure or signal during call_connect, for
example) would drive xprt_release() ->
xprt_rdma_free_slot() -> kref_put against a refcount of
zero, saturating refcount_t and stranding the slot.
- The Send-side reference is taken only after WR prep
succeeds. A mapping failure in rpcrdma_prepare_send_sges()
runs rpcrdma_sendctx_cancel(), which DMA-unmaps the sendctx
and clears sc_req without touching rl_kref. The sendctx
ring walks in rpcrdma_sendctx_put_locked() and
rpcrdma_sendctxs_destroy() skip entries with sc_req == NULL,
so a burst of -EIO marshal failures cannot hold reqs off
rb_send_bufs.
- The release callback re-arms rl_kref so the next consumer
enters with the invariant satisfied.
Replies now complete the RPC directly. rpcrdma_reply_handler()
calls rpcrdma_complete_rqst() in place of kref_put on the
non-LocalInv branch. The LocalInv branch already completes the
RPC from frwr_unmap_async() and is unaffected.
Because Send-side references can now outlive RPC completion,
connection teardown drains sendctx entries whose unsignaled
Sends never had a later signaled completion to walk the ring.
rpcrdma_sendctxs_destroy() walks the active range and runs
rpcrdma_sendctx_unmap() on each entry with a non-NULL sc_req
before the request buffers are reset, and is moved ahead of
rpcrdma_reqs_reset() in rpcrdma_xprt_disconnect() so the reqs
are still in their pre-reset state when the Send-side refs are
released.
The drain creates a teardown-ordering hazard on the backchannel
path. With the new lifetime, releasing a bc_prealloc req from
rpcrdma_req_release() re-adds it to bc_pa_list. The disconnect
in xprt_rdma_destroy() runs after xprt_destroy_backchannel() has
already emptied bc_pa_list, so the drained reqs would otherwise
leak. xprt_rdma_destroy() now runs xprt_rdma_bc_destroy(xprt, 0)
a second time after the disconnect to reclaim them.
xprtrdma: Decouple req recycling from RPC completion
rl_kref formerly served two distinct lifetimes through a single
refcount: it gated when a Reply could wake its RPC task, and it
gated when an rpcrdma_req could return to its free pool. The
marshal path took the Send-side reference only when SGEs needed
DMA-unmap (sc_unmap_count > 0), which made a Send carrying only
pre-registered buffers an exception: the Reply handler dropped
rl_kref from 1 to 0 and freed the req while the HCA might still
be DMA-reading from its send buffer.
Give rl_kref a narrower job. The RPC layer takes one reference
when slot allocation hands a req out. rpcrdma_prepare_send_sges()
takes a Send-side reference unconditionally after WR preparation
succeeds. xprt_rdma_free_slot() and xprt_rdma_bc_free_rqst() drop
the RPC-layer reference; rpcrdma_sendctx_unmap() drops the
Send-side reference. The req returns to its free pool only after
both owners have signed off.
The existing kref_init(&req->rl_kref) call in
rpcrdma_prepare_send_sges() is removed. Initialization moves to
the slot-allocation paths (xprt_rdma_alloc_slot and
rpcrdma_bc_rqst_get), and the release callback re-arms rl_kref
before the req returns to a free pool. A re-init in the marshal
path would discard the RPC-layer reference that already exists
on entry.
Three invariants follow:
- Any rpcrdma_req held by an rpc_rqst has rl_kref >= 1.
xprt_rdma_alloc_slot(), rpcrdma_bc_rqst_get(), and the
backlog-wake branch in xprt_rdma_alloc_slot() each kref_init
rl_kref before publishing the req. Without this invariant,
an RPC task that aborts between slot allocation and marshal
(gss_refresh failure or signal during call_connect, for
example) would drive xprt_release() ->
xprt_rdma_free_slot() -> kref_put against a refcount of
zero, saturating refcount_t and stranding the slot.
- The Send-side reference is taken only after WR prep
succeeds. A mapping failure in rpcrdma_prepare_send_sges()
runs rpcrdma_sendctx_cancel(), which DMA-unmaps the sendctx
and clears sc_req without touching rl_kref. The sendctx
ring walks in rpcrdma_sendctx_put_locked() and
rpcrdma_sendctxs_destroy() skip entries with sc_req == NULL,
so a burst of -EIO marshal failures cannot hold reqs off
rb_send_bufs.
- The release callback re-arms rl_kref so the next consumer
enters with the invariant satisfied.
Replies now complete the RPC directly. rpcrdma_reply_handler()
calls rpcrdma_complete_rqst() in place of kref_put on the
non-LocalInv branch. The LocalInv branch already completes the
RPC from frwr_unmap_async() and is unaffected.
Because Send-side references can now outlive RPC completion,
connection teardown drains sendctx entries whose unsignaled
Sends never had a later signaled completion to walk the ring.
rpcrdma_sendctxs_destroy() walks the active range and runs
rpcrdma_sendctx_unmap() on each entry with a non-NULL sc_req
before the request buffers are reset, and is moved ahead of
rpcrdma_reqs_reset() in rpcrdma_xprt_disconnect() so the reqs
are still in their pre-reset state when the Send-side refs are
released.
The drain creates a teardown-ordering hazard on the backchannel
path. With the new lifetime, releasing a bc_prealloc req from
rpcrdma_req_release() re-adds it to bc_pa_list. The disconnect
in xprt_rdma_destroy() runs after xprt_destroy_backchannel() has
already emptied bc_pa_list, so the drained reqs would otherwise
leak. xprt_rdma_destroy() now runs xprt_rdma_bc_destroy(xprt, 0)
a second time after the disconnect to reclaim them.
Published:
2026-08-15
Score:
n/a
EPSS:
< 1% Very Low
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
Analysis and contextual insights are available on OpenCVE Cloud.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
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| Linux | Linux | affected |
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No data.
No data.
No data available yet.
Remediation
No vendor fix or workaround currently provided.
Additional remediation guidance may be available on OpenCVE Cloud.
Tracking
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Advisories
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References
History
Sat, 15 Aug 2026 12:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-362 CWE-416 |
Sat, 15 Aug 2026 06:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: xprtrdma: Decouple req recycling from RPC completion rl_kref formerly served two distinct lifetimes through a single refcount: it gated when a Reply could wake its RPC task, and it gated when an rpcrdma_req could return to its free pool. The marshal path took the Send-side reference only when SGEs needed DMA-unmap (sc_unmap_count > 0), which made a Send carrying only pre-registered buffers an exception: the Reply handler dropped rl_kref from 1 to 0 and freed the req while the HCA might still be DMA-reading from its send buffer. Give rl_kref a narrower job. The RPC layer takes one reference when slot allocation hands a req out. rpcrdma_prepare_send_sges() takes a Send-side reference unconditionally after WR preparation succeeds. xprt_rdma_free_slot() and xprt_rdma_bc_free_rqst() drop the RPC-layer reference; rpcrdma_sendctx_unmap() drops the Send-side reference. The req returns to its free pool only after both owners have signed off. The existing kref_init(&req->rl_kref) call in rpcrdma_prepare_send_sges() is removed. Initialization moves to the slot-allocation paths (xprt_rdma_alloc_slot and rpcrdma_bc_rqst_get), and the release callback re-arms rl_kref before the req returns to a free pool. A re-init in the marshal path would discard the RPC-layer reference that already exists on entry. Three invariants follow: - Any rpcrdma_req held by an rpc_rqst has rl_kref >= 1. xprt_rdma_alloc_slot(), rpcrdma_bc_rqst_get(), and the backlog-wake branch in xprt_rdma_alloc_slot() each kref_init rl_kref before publishing the req. Without this invariant, an RPC task that aborts between slot allocation and marshal (gss_refresh failure or signal during call_connect, for example) would drive xprt_release() -> xprt_rdma_free_slot() -> kref_put against a refcount of zero, saturating refcount_t and stranding the slot. - The Send-side reference is taken only after WR prep succeeds. A mapping failure in rpcrdma_prepare_send_sges() runs rpcrdma_sendctx_cancel(), which DMA-unmaps the sendctx and clears sc_req without touching rl_kref. The sendctx ring walks in rpcrdma_sendctx_put_locked() and rpcrdma_sendctxs_destroy() skip entries with sc_req == NULL, so a burst of -EIO marshal failures cannot hold reqs off rb_send_bufs. - The release callback re-arms rl_kref so the next consumer enters with the invariant satisfied. Replies now complete the RPC directly. rpcrdma_reply_handler() calls rpcrdma_complete_rqst() in place of kref_put on the non-LocalInv branch. The LocalInv branch already completes the RPC from frwr_unmap_async() and is unaffected. Because Send-side references can now outlive RPC completion, connection teardown drains sendctx entries whose unsignaled Sends never had a later signaled completion to walk the ring. rpcrdma_sendctxs_destroy() walks the active range and runs rpcrdma_sendctx_unmap() on each entry with a non-NULL sc_req before the request buffers are reset, and is moved ahead of rpcrdma_reqs_reset() in rpcrdma_xprt_disconnect() so the reqs are still in their pre-reset state when the Send-side refs are released. The drain creates a teardown-ordering hazard on the backchannel path. With the new lifetime, releasing a bc_prealloc req from rpcrdma_req_release() re-adds it to bc_pa_list. The disconnect in xprt_rdma_destroy() runs after xprt_destroy_backchannel() has already emptied bc_pa_list, so the drained reqs would otherwise leak. xprt_rdma_destroy() now runs xprt_rdma_bc_destroy(xprt, 0) a second time after the disconnect to reclaim them. | |
| Title | xprtrdma: Decouple req recycling from RPC completion | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-08-15T05:57:14.412Z
Reserved: 2026-08-09T03:40:39.934Z
Link: CVE-2026-72473
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-08-15T06:22:21.423
Modified: 2026-08-15T06:22:21.423
Link: CVE-2026-72473
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-08-15T12:30:07Z