Patch "lib: alloc_tag_module_unload must wait for pending kfree_rcu calls" has been added to the 6.11-stable tree

DISCUSSION Suren Baghdasaryan 1 participant 1 message Nov 1, 2024 1 message not in the archive Stable branch

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Suren Baghdasaryan

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2024-11-01 15:24 UTC #1 lore raw

Quoted 11 lines · Sasha Levin

This is a note to let you know that I've just added the patch titled
lib: alloc_tag_module_unload must wait for pending kfree_rcu calls
to the 6.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
lib-alloc_tag_module_unload-must-wait-for-pending-kf.patch
and it can be found in the queue-6.11 subdirectory.

Thanks Sasha! Could you please double-check that the prerequisite patch https://lore.kernel.org/all/[email protected]/
was also picked up? I don't see it in the queue-6.11 directory. Without that patch this one will cause build errors, that's why I sent them as a patchset.
Thanks,
Suren.

Quoted 65 lines

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
commit 536dfe685ebd28b27ebfbc3d4b9168207b7e28a3
Author: Florian Westphal <[email protected]>
Date:   Mon Oct 7 22:52:24 2024 +0200
lib: alloc_tag_module_unload must wait for pending kfree_rcu calls
[ Upstream commit dc783ba4b9df3fb3e76e968b2cbeb9960069263c ]
Ben Greear reports following splat:
------------[ cut here ]------------
net/netfilter/nf_nat_core.c:1114 module nf_nat func:nf_nat_register_fn has 256 allocated at module unload
WARNING: CPU: 1 PID: 10421 at lib/alloc_tag.c:168 alloc_tag_module_unload+0x22b/0x3f0 Modules linked in: nf_nat(-) btrfs ufs qnx4 hfsplus hfs minix vfat msdos fat
...
Hardware name: Default string Default string/SKYBAY, BIOS 5.12 08/04/2020
RIP: 0010:alloc_tag_module_unload+0x22b/0x3f0
codetag_unload_module+0x19b/0x2a0
? codetag_load_module+0x80/0x80
nf_nat module exit calls kfree_rcu on those addresses, but the free operation is likely still pending by the time alloc_tag checks for leaks.
Wait for outstanding kfree_rcu operations to complete before checking resolves this warning.
Reproducer:
unshare -n iptables-nft -t nat -A PREROUTING -p tcp grep nf_nat /proc/allocinfo # will list 4 allocations rmmod nft_chain_nat
rmmod nf_nat # will WARN.
[[email protected]: add comment]
Link https://lkml.kernel.org/r/[email protected] open here
Fixes a473573964e5 ("lib: code tagging module support")
Signed-off-by Florian Westphal <[email protected]>
Reported-by Ben Greear <[email protected]>
Closes https://lore.kernel.org/netdev/[email protected]/ open here
Cc Uladzislau Rezki <[email protected]>
Cc Vlastimil Babka <[email protected]>
Cc Suren Baghdasaryan <[email protected]>
Cc Kent Overstreet <[email protected]>
Cc <[email protected]>
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
lib/codetag.c +3 -0
index afa8a2d4f3173..d1fbbb7c2ec3d 100644
@@ -228,6 +228,9 @@ bool codetag_unload_module(struct module *mod)
        if (!mod)
                return true;
 
+       /* await any module's kfree_rcu() operations to complete */
+       kvfree_rcu_barrier();
+
        mutex_lock(&codetag_lock);
        list_for_each_entry(cttype, &codetag_types, link) {
                struct codetag_module *found = NULL;