CVE-2026-52995

Summary

In the Linux kernel, the following vulnerability has been resolved:

net/rds: zero per-item info buffer before handing it to visitors

rds_for_each_conn_info() and rds_walk_conn_path_info() both hand a caller-allocated on-stack u64 buffer to a per-connection visitor and then copy the full item_len bytes back to user space via rds_info_copy() regardless of how much of the buffer the visitor actually wrote.

rds_ib_conn_info_visitor() and rds6_ib_conn_info_visitor() only write a subset of their output struct when the underlying rds_connection is not in state RDS_CONN_UP (src/dst addr, tos, sl and the two GIDs via explicit memsets). Several u32 fields (max_send_wr, max_recv_wr, max_send_sge, rdma_mr_max, rdma_mr_size, cache_allocs) and the 2-byte alignment hole between sl and cache_allocs remain as whatever stack contents preceded the visitor call and are then memcpy_to_user()'d out to user space.

struct rds_info_rdma_connection and struct rds6_info_rdma_connection are the only rds_info_* structs in include/uapi/linux/rds.h that are not marked attribute((packed)), so they have a real alignment hole. The other info visitors (rds_conn_info_visitor, rds6_conn_info_visitor, rds_tcp_tc_info, …) write all fields of their packed output struct today and are not known to be vulnerable, but a future visitor that adds a conditional write-path would have the same bug.

Reproduction on a kernel built without CONFIG_INIT_STACK_ALL_ZERO=y: a local unprivileged user opens AF_RDS, sets SO_RDS_TRANSPORT=IB, binds to a local address on an RDMA-capable netdev (rxe soft-RoCE on any netdev is sufficient), sendto()'s any peer on the same subnet (fails cleanly but installs an rds_connection in the global hash in RDS_CONN_CONNECTING), then calls getsockopt(SOL_RDS, RDS_INFO_IB_CONNECTIONS). The returned 68-byte item contains 26 bytes of stack garbage including kernel text/data pointers:

0..7   0a 63 00 01 0a 63 00 02     src=10.99.0.1 dst=10.99.0.2
8..39  00 ...                      gids (memset-zeroed)
40..47 e0 92 a3 81 ff ff ff ff     kernel pointer (max_send_wr)
48..55 7f 37 b5 81 ff ff ff ff     kernel pointer (rdma_mr_max)
56..59 01 00 08 00                 rdma_mr_size (garbage)
60..61 00 00                       tos, sl
62..63 00 00                       alignment padding
64..67 18 00 00 00                 cache_allocs (garbage)

Fix by zeroing the per-item buffer in both rds_for_each_conn_info() and rds_walk_conn_path_info() before invoking the visitor. This covers the IPv4/IPv6 IB visitors and hardens all current and future visitors against the same class of bug.

No functional change for visitors that fully populate their output.

Changes in v2:

• retarget at the net tree (subject prefix "[PATCH net v2]", net/rds: prefix in the title)
• pick up Reviewed-by tags from Sharath Srinivasan and Allison Henderson

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/81651e9d7dea1c048d2952f57632a042931d7b43
• https://git.kernel.org/stable/c/0797b2e6901827694aa9c34c4c72118c8c97fba1
• https://git.kernel.org/stable/c/5e67cc262afb384e835c3327e9d954eeaedc6a87
• https://git.kernel.org/stable/c/b6ba93a7b71ed443c9843eb12d27ed86f1e52694
• https://git.kernel.org/stable/c/c7cb9eed8215a790f052f49cdccf577720d2bb62
• https://git.kernel.org/stable/c/91ce1bb6e4194dc2321748f68145359dcf86e350
• https://git.kernel.org/stable/c/912ba2e5704fdb8bc5decda96dfc1a57838f0099
• https://git.kernel.org/stable/c/c88eb7e8d8397a8c1db59c425332c5a30b2a1682

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