In the Linux kernel, the following vulnerability has been resolved:
rds: ib: Clear the sg list when mapping an MR fails
rds_ib_map_frmr() stores the caller's scatterlist in the MR before DMA mapping and registration can fail. On failure, __rds_rdma_map() unpins the pages and frees the scatterlist, but rds_ib_free_frmr() can still return the MR to the pool with the stale pointer set.
This leaves the pool with a dangling scatterlist and can lead to local privilege escalation. KASAN detects the resulting use-after-free when the MR is later torn down:
BUG: KASAN: slab-use-after-free in __rds_ib_teardown_mr Read of size 8
Call Trace: __rds_ib_teardown_mr rds_ib_unreg_frmr rds_ib_flush_mr_pool rds_ib_flush_mrs rds_free_mr rds_setsockopt
Store the scatterlist in the MR only after DMA mapping succeeds. If DMA mapping fails, return directly while the MR fields remain clear; the caller keeps ownership of the scatterlist and its pinned pages. If a later registration step fails, unmap the scatterlist and clear the MR fields before returning.
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