swh:1:snp:c3bf2749e3476071fa748f67b0ffa2fdc5fe49d9
Revision f2764bd4f6a8dffaec3e220728385d9756b3c2cb authored by Florian Westphal on 16 April 2021, 19:29:13 UTC, committed by David S. Miller on 17 April 2021, 00:01:04 UTC
When I added support to allow generic netlink multicast groups to be restricted to subscribers with CAP_NET_ADMIN I was unaware that a genl_bind implementation already existed in the past. It was reverted due to ABBA deadlock: 1. ->netlink_bind gets called with the table lock held. 2. genetlink bind callback is invoked, it grabs the genl lock. But when a new genl subsystem is (un)registered, these two locks are taken in reverse order. One solution would be to revert again and add a comment in genl referring 1e82a62fec613, "genetlink: remove genl_bind"). This would need a second change in mptcp to not expose the raw token value anymore, e.g. by hashing the token with a secret key so userspace can still associate subflow events with the correct mptcp connection. However, Paolo Abeni reminded me to double-check why the netlink table is locked in the first place. I can't find one. netlink_bind() is already called without this lock when userspace joins a group via NETLINK_ADD_MEMBERSHIP setsockopt. Same holds for the netlink_unbind operation. Digging through the history, commit f773608026ee1 ("netlink: access nlk groups safely in netlink bind and getname") expanded the lock scope. commit 3a20773beeeeade ("net: netlink: cap max groups which will be considered in netlink_bind()") ... removed the nlk->ngroups access that the lock scope extension was all about. Reduce the lock scope again and always call ->netlink_bind without the table lock. The Fixes tag should be vs. the patch mentioned in the link below, but that one got squash-merged into the patch that came earlier in the series. Fixes: 4d54cc32112d8d ("mptcp: avoid lock_fast usage in accept path") Link: https://lore.kernel.org/mptcp/20210213000001.379332-8-mathew.j.martineau@linux.intel.com/T/#u Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: Xin Long <lucien.xin@gmail.com> Cc: Johannes Berg <johannes.berg@intel.com> Cc: Sean Tranchetti <stranche@codeaurora.org> Cc: Paolo Abeni <pabeni@redhat.com> Cc: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
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Tip revision: d1221cea11fca0f6946bdd032a45b22cecfc0f99 authored by Linus Torvalds on 13 September 2022, 13:11:38 UTC
Merge tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Merge tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Tip revision: d1221ce
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.clang-format | -rw-r--r-- | 16.4 KB |
.cocciconfig | -rw-r--r-- | 59 bytes |
.get_maintainer.ignore | -rw-r--r-- | 71 bytes |
.gitattributes | -rw-r--r-- | 62 bytes |
.gitignore | -rw-r--r-- | 1.9 KB |
.mailmap | -rw-r--r-- | 18.7 KB |
COPYING | -rw-r--r-- | 496 bytes |
CREDITS | -rw-r--r-- | 98.3 KB |
Kbuild | -rw-r--r-- | 1.3 KB |
Kconfig | -rw-r--r-- | 555 bytes |
MAINTAINERS | -rw-r--r-- | 577.5 KB |
Makefile | -rw-r--r-- | 64.7 KB |
README | -rw-r--r-- | 727 bytes |
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