Re: [PATCH net] rds: mark snapshot pages dirty in rds_info_getsockopt()
From: Allison Henderson <achender@kernel.org>
Date: 2026-06-09 08:02:02
Also in:
linux-rdma, lkml
On Mon, 2026-06-08 at 02:32 -0700, Breno Leitao wrote:
rds_info_getsockopt() pins the destination user pages with FOLL_WRITE and
the RDS_INFO_* producers memcpy the snapshot into them through
kmap_atomic(). Because that copy goes through the kernel direct map, the
dirty bit on the user PTE is never set, so unpin_user_pages() releases the
pages without marking them dirty. A file-backed destination page can then
be reclaimed without writeback, silently discarding the copied data.
Use unpin_user_pages_dirty_lock() with make_dirty=true so the modified
pages are marked dirty before they are unpinned.
Fixes: a8c879a7ee98 ("RDS: Info and stats")
Signed-off-by: Breno Leitao <leitao@debian.org>Hi Breno, Thanks for adding the Fixes tag. One thing though: now that this is standalone, it collides with "[PATCH net-next v3 2/2] rds: convert to getsockopt_iter" since both rewrite the same unpin in the out: block of rds_info_getsockopt(). Easiest on everyone is to just keep it folded into the net-next series as a three-patch set, rather than splitting the fix out to net. With that, you can add my: Reviewed-by: Allison Henderson <achender@kernel.org> Thanks! Allison
quoted hunk ↗ jump to hunk
--- net/rds/info.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/net/rds/info.c b/net/rds/info.c index f1b29994934a..17061f6ff74e 100644 --- a/net/rds/info.c +++ b/net/rds/info.c@@ -235,7 +235,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval, out: if (pages) - unpin_user_pages(pages, nr_pages); + unpin_user_pages_dirty_lock(pages, nr_pages, true); kfree(pages); return ret;--- base-commit: 9772589b57e44aedc240211c5c3f7a684a034d3a change-id: 20260608-rds_fix-92d6c7f04fe2 Best regards,