From: Caleb Sander Mateos csander@purestorage.com
[ Upstream commit ccb8a3c08adf8121e2afb8e704f007ce99324d79 ]
The PI tuple must be contained within the metadata value, so validate that pi_offset + pi_tuple_size <= metadata_size. This guards against block drivers that report invalid pi_offset values.
Signed-off-by: Caleb Sander Mateos csander@purestorage.com Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
## Summary
### Problem Being Fixed The commit fixes an **incomplete bounds validation bug** in the block layer's integrity limit validation code. When the PI (Protection Information) tuple can be placed at a non-zero offset within the metadata buffer (a feature added in kernel 6.9), the validation check only verified that `pi_tuple_size <= metadata_size`, but **completely ignored the pi_offset**.
This is mathematically incorrect. If: - `metadata_size = 8` bytes - `pi_tuple_size = 8` bytes - `pi_offset = 4` bytes
The old check (`8 > 8`) passes, but the PI tuple would extend 4 bytes beyond the buffer boundary, potentially causing out-of-bounds memory access.
### Why It Matters to Stable Users - **Data Integrity Risk**: Block layer integrity/PI is used in enterprise storage environments (NVMe, SAS with T10 PI) - **Defense Against Buggy Drivers**: The fix prevents the kernel from accepting invalid configurations from misbehaving block drivers - **Potential for Memory Corruption**: Without this validation, accessing PI data could read/write beyond buffer bounds
### Stable Kernel Criteria Assessment
| Criterion | Met? | Notes | |-----------|------|-------| | Obviously correct | ✅ | Mathematical correctness: offset + size must fit in buffer | | Fixes real bug | ✅ | Incomplete bounds check could allow invalid configurations | | Small scope | ✅ | 4 lines changed, single file | | No new features | ✅ | Only strengthens existing validation | | No API changes | ✅ | No user-visible changes |
### Risk vs Benefit
**Risk**: Extremely low - The change only makes validation stricter - Can only reject configurations that were previously (incorrectly) accepted - Any configuration rejected by the new check was already semantically invalid and potentially dangerous
**Benefit**: Moderate to high - Prevents kernel from accepting invalid integrity configurations - Guards against memory corruption in PI-enabled storage stacks - Important for enterprise environments using DIF/PI
### Concerns
**Applicability**: The `pi_offset` field was introduced in kernel 6.9 (commit 60d21aac52e2). This fix is only applicable to stable kernels 6.9.y and later.
**Dependencies**: None - this is a standalone validation fix.
### Quality Indicators - Reviewed-by: Christoph Hellwig (highly respected kernel developer) - Signed-off-by: Jens Axboe (block layer maintainer) - Part of a series of validation improvements (similar commit for `interval_exp`) - No follow-up fixes needed
The fix is small, surgical, obviously correct, and addresses a real validation gap that could lead to memory safety issues. It meets all stable kernel criteria.
**YES**
block/blk-settings.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/block/blk-settings.c b/block/blk-settings.c index d74b13ec8e54..f2c1940fe6f1 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -148,10 +148,9 @@ static int blk_validate_integrity_limits(struct queue_limits *lim) return -EINVAL; }
- if (bi->pi_tuple_size > bi->metadata_size) { - pr_warn("pi_tuple_size (%u) exceeds metadata_size (%u)\n", - bi->pi_tuple_size, - bi->metadata_size); + if (bi->pi_offset + bi->pi_tuple_size > bi->metadata_size) { + pr_warn("pi_offset (%u) + pi_tuple_size (%u) exceeds metadata_size (%u)\n", + bi->pi_offset, bi->pi_tuple_size, bi->metadata_size); return -EINVAL; }