[PATCH stable 6.1 0/2] devlink: Fix RCU stall when unregistering a devlink instance

[Ido Schimmel <idosch@nvidia.com>]

Upstream commit c2368b19807a ("net: devlink: introduce "unregistering"
mark and use it during devlinks iteration") in v6.0 introduced a race
when unregistering a devlink instance that can result in RCU stalls and
in the system completely locking up. Exact details and reproducer can be
found here [1]. The bug was inadvertently fixed in v6.3 by upstream
commit d77278196441 ("devlink: bump the instance index directly when
iterating").

This patchset fixes the bug by backporting the second commit and a
related dependency from v6.3 to v6.1.y while adjusting them to the
devlink file structure in v6.1.y (net/devlink/{core.c,devl_internal.h}
-> net/devlink/leftover.c).

Tested by running the devlink tests under
tools/testing/selftests/drivers/net/netdevsim/ and the reproducer
mentioned in [1].

[1] https://lore.kernel.org/stable/20241001112035.973187-1-idosch@nvidia.com/

Jakub Kicinski (2):
  devlink: drop the filter argument from devlinks_xa_find_get
  devlink: bump the instance index directly when iterating

 net/devlink/leftover.c | 40 ++++++++++------------------------------
 1 file changed, 10 insertions(+), 30 deletions(-)

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2.47.0