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dc58e40274
[ Upstream commit edbd82c5fb ]
Following splat gets triggered when nfnetlink monitor is running while
xtables-nft selftests are running:
net/netfilter/nf_tables_api.c:1272 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
1 lock held by xtables-nft-mul/27006:
#0: 00000000e0f85be9 (&net->nft.commit_mutex){+.+.}, at: nf_tables_valid_genid+0x1a/0x50
Call Trace:
nf_tables_fill_chain_info.isra.45+0x6cc/0x6e0
nf_tables_chain_notify+0xf8/0x1a0
nf_tables_commit+0x165c/0x1740
nf_tables_fill_chain_info() can be called both from dumps (rcu read locked)
or from the transaction path if a userspace process subscribed to nftables
notifications.
In the 'table dump' case, rcu_access_pointer() cannot be used: We do not
hold transaction mutex so the pointer can be NULLed right after the check.
Just unconditionally fetch the value, then have the helper return
immediately if its NULL.
In the notification case we don't hold the rcu read lock, but updates are
prevented due to transaction mutex. Use rcu_dereference_check() to make lockdep
aware of this.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.