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RHEL9 has a number of places that are accessing the inode->i_flctx field without using a smp_load_acquire. This is required to ensure that the caller doesn't see a partially-initialized structure.
Pull in commit 401a8b8fd5acd and the follow-on patches.
We may be technically breaking kABI with this patch:
2f6076aad206 fs/lock: add 2 callbacks to lock_manager_operations to resolve conflict
This grows the lock_manager_operations struct, so if anyone is using an out of tree lock manager (something akin to nfsd or lockd), then this could break for them. @bcodding thinks there might be a chance that GPFS is setting this field in some cases, and is going to try to confirm whether that's the case. That sounds wrong to me, but it's worth investigating before we merge this. Stay tuned.
Comment 9Benjamin Coddington
2023-03-28 12:04:39 UTC
(In reply to Jeff Layton from comment #6)
> This grows the lock_manager_operations struct, so if anyone is using an out
> of tree lock manager (something akin to nfsd or lockd), then this could
> break for them. @bcodding thinks there might be a chance that
> GPFS is setting this field in some cases, and is going to try to confirm
> whether that's the case. That sounds wrong to me, but it's worth
> investigating before we merge this. Stay tuned.
We did find gpfs is setting lm_ops in some cases, Jeff has modified the work to set a flag if we're going to be accessing the new offsets in the struct. Its possible we don't need to technically do this due to the new kABI rules for RHEL-9, but doing it also makes things safer if older versions of modules are loaded.
It does seem like we should be able to restrict older/non-compatible out-of-tree-modules using structs that have changed with some versioning magic, but I'm not sure how that works. Do we want to try to get a kABI SME to look at this?
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory (Important: kernel security, bug fix, and enhancement update), and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHSA-2023:6583