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RDMA/ucma: Allow path records to exactly fit the output buffer

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ucma_query_path() emits a path record only when the remaining output
buffer is strictly larger than struct ib_path_rec_data. A buffer sized
exactly for the response header and N complete records therefore gets
only N - 1 records, while resp->num_paths still advertises N. A caller
sizing its buffer for a single record gets a header claiming one path
and no path data at all.

ucma_query_ib_service() in the same file computes the record count with
a plain division and so accepts an exact fit; make ucma_query_path()
behave the same way.

Current librdmacm is unaffected because it always sizes the response for
six records while the kernel currently reports at most two paths. Other
users of the UAPI that provide an exactly sized buffer can observe the
truncated response.

Fixes: ac53b264b2 ("RDMA/ucma: Support querying when IB paths are not reversible")
Signed-off-by: Serhat Kumral <serhatkumral1@gmail.com>
Link: https://patch.msgid.link/20260806201358.147478-1-serhatkumral1@gmail.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
This commit is contained in:
Serhat Kumral 2026-08-06 23:13:58 +03:00 committed by Jason Gunthorpe
parent 60a42d5101
commit 8049741ac9
1 changed files with 1 additions and 1 deletions
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2
drivers/infiniband/core/ucma.c
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@ -951,7 +951,7 @@ static ssize_t ucma_query_path(struct ucma_context *ctx,
resp->num_paths = ctx->cm_id->route.num_pri_alt_paths;
for (i = 0, out_len -= sizeof(*resp);
i < resp->num_paths && out_len > sizeof(struct ib_path_rec_data);
i < resp->num_paths && out_len >= sizeof(struct ib_path_rec_data);
i++, out_len -= sizeof(struct ib_path_rec_data)) {
struct sa_path_rec *rec = &ctx->cm_id->route.path_rec[i];