| 919dc320 | 01-Aug-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: skip PKCS#7 parser when keyring is empty
If an fsverity builtin signature is given for a file but the
".fs-verity" keyring is empty, there's no real reason to run the PKCS#7
parser. Skip
fsverity: skip PKCS#7 parser when keyring is empty
If an fsverity builtin signature is given for a file but the
".fs-verity" keyring is empty, there's no real reason to run the PKCS#7
parser. Skip this to avoid the PKCS#7 attack surface when builtin
signature support is configured into the kernel but is not being used.
This is a hardening improvement, not a fix per se, but I've added
Fixes and Cc stable to get it out to more users.
Fixes: 432434c9f8e1 ("fs-verity: support builtin file signatures")
Cc: stable@vger.kernel.org
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lore.kernel.org/r/20230820173237.2579-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| 456ae5fe | 05-Jul-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: move sysctl registration out of signature.c
Currently the registration of the fsverity sysctls happens in
signature.c, which couples it to CONFIG_FS_VERITY_BUILTIN_SIGNATURES.
This makes
fsverity: move sysctl registration out of signature.c
Currently the registration of the fsverity sysctls happens in
signature.c, which couples it to CONFIG_FS_VERITY_BUILTIN_SIGNATURES.
This makes it hard to add new sysctls unrelated to builtin signatures.
Also, some users have started checking whether the directory
/proc/sys/fs/verity exists as a way to tell whether fsverity is
supported. This isn't the intended method; instead, the existence of
/sys/fs/$fstype/features/verity should be checked, or users should just
try to use the fsverity ioctls. Regardless, it should be made to work
as expected without a dependency on CONFIG_FS_VERITY_BUILTIN_SIGNATURES.
Therefore, move the sysctl registration into init.c. With
CONFIG_FS_VERITY_BUILTIN_SIGNATURES, nothing changes. Without it, but
with CONFIG_FS_VERITY, an empty list of sysctls is now registered.
Link: https://lore.kernel.org/r/20230705212743.42180-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| e77000cc | 05-Jul-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: simplify handling of errors during initcall
Since CONFIG_FS_VERITY is a bool, not a tristate, fs/verity/ can only be
builtin or absent entirely; it can't be a loadable module. Therefore,
fsverity: simplify handling of errors during initcall
Since CONFIG_FS_VERITY is a bool, not a tristate, fs/verity/ can only be
builtin or absent entirely; it can't be a loadable module. Therefore,
the error code that gets returned from the fsverity_init() initcall is
never used. If any part of the initcall does fail, which should never
happen, the kernel will be left in a bad state.
Following the usual convention for builtin code, just panic the kernel
if any of part of the initcall fails.
Link: https://lore.kernel.org/r/20230705212743.42180-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| 672d6ef4 | 19-Jun-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: improve documentation for builtin signature support
fsverity builtin signatures (CONFIG_FS_VERITY_BUILTIN_SIGNATURES) aren't
the only way to do signatures with fsverity, and they have some
fsverity: improve documentation for builtin signature support
fsverity builtin signatures (CONFIG_FS_VERITY_BUILTIN_SIGNATURES) aren't
the only way to do signatures with fsverity, and they have some major
limitations. Yet, more users have tried to use them, e.g. recently by
https://github.com/ostreedev/ostree/pull/2640. In most cases this seems
to be because users aren't sufficiently familiar with the limitations of
this feature and what the alternatives are.
Therefore, make some updates to the documentation to try to clarify the
properties of this feature and nudge users in the right direction.
Note that the Integrity Policy Enforcement (IPE) LSM, which is not yet
upstream, is planned to use the builtin signatures. (This differs from
IMA, which uses its own signature mechanism.) For that reason, my
earlier patch "fsverity: mark builtin signatures as deprecated"
(https://lore.kernel.org/r/20221208033548.122704-1-ebiggers@kernel.org),
which marked builtin signatures as "deprecated", was controversial.
This patch therefore stops short of marking the feature as deprecated.
I've also revised the language to focus on better explaining the feature
and what its alternatives are.
Link: https://lore.kernel.org/r/20230620041937.5809-1-ebiggers@kernel.org
Reviewed-by: Colin Walters <walters@verbum.org>
Reviewed-by: Luca Boccassi <bluca@debian.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| 74836ecb | 12-Jun-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: rework fsverity_get_digest() again
Address several issues with the calling convention and documentation of
fsverity_get_digest():
- Make it provide the hash algorithm as either a FS_VERIT
fsverity: rework fsverity_get_digest() again
Address several issues with the calling convention and documentation of
fsverity_get_digest():
- Make it provide the hash algorithm as either a FS_VERITY_HASH_ALG_*
value or HASH_ALGO_* value, at the caller's choice, rather than only a
HASH_ALGO_* value as it did before. This allows callers to work with
the fsverity native algorithm numbers if they want to. HASH_ALGO_* is
what IMA uses, but other users (e.g. overlayfs) should use
FS_VERITY_HASH_ALG_* to match fsverity-utils and the fsverity UAPI.
- Make it return the digest size so that it doesn't need to be looked up
separately. Use the return value for this, since 0 works nicely for
the "file doesn't have fsverity enabled" case. This also makes it
clear that no other errors are possible.
- Rename the 'digest' parameter to 'raw_digest' and clearly document
that it is only useful in combination with the algorithm ID. This
hopefully clears up a point of confusion.
- Export it to modules, since overlayfs will need it for checking the
fsverity digests of lowerdata files
(https://lore.kernel.org/r/dd294a44e8f401e6b5140029d8355f88748cd8fd.1686565330.git.alexl@redhat.com).
Acked-by: Mimi Zohar <zohar@linux.ibm.com> # for the IMA piece
Link: https://lore.kernel.org/r/20230612190047.59755-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| 13e2408d | 03-Jun-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: simplify error handling in verify_data_block()
Clean up the error handling in verify_data_block() to (a) eliminate the
'err' variable which has caused some confusion because the function
a
fsverity: simplify error handling in verify_data_block()
Clean up the error handling in verify_data_block() to (a) eliminate the
'err' variable which has caused some confusion because the function
actually returns a bool, (b) reduce the compiled code size slightly, and
(c) execute one fewer branch in the success case.
Link: https://lore.kernel.org/r/20230604022312.48532-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| d1f0c5ea | 03-Jun-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: don't use bio_first_page_all() in fsverity_verify_bio()
bio_first_page_all(bio)->mapping->host is not compatible with large
folios, since the first page of the bio is not necessarily the h
fsverity: don't use bio_first_page_all() in fsverity_verify_bio()
bio_first_page_all(bio)->mapping->host is not compatible with large
folios, since the first page of the bio is not necessarily the head page
of the folio, and therefore it might not have the mapping pointer set.
Therefore, move the dereference of ->mapping->host into
verify_data_blocks(), which works with a folio.
(Like the commit that this Fixes, this hasn't actually been tested with
large folios yet, since the filesystems that use fs/verity/ don't
support that yet. But based on code review, I think this is needed.)
Fixes: 5d0f0e57ed90 ("fsverity: support verifying data from large folios")
Link: https://lore.kernel.org/r/20230604022101.48342-1-ebiggers@kernel.org
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| 32ab3c5e | 03-Jun-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: constify fsverity_hash_alg
Now that fsverity_hash_alg doesn't have an embedded mempool, it can be
'const' almost everywhere. Add it.
Link: https://lore.kernel.org/r/20230604022348.48658-
fsverity: constify fsverity_hash_alg
Now that fsverity_hash_alg doesn't have an embedded mempool, it can be
'const' almost everywhere. Add it.
Link: https://lore.kernel.org/r/20230604022348.48658-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| 04839139 | 06-Apr-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: reject FS_IOC_ENABLE_VERITY on mode 3 fds
Commit 56124d6c87fd ("fsverity: support enabling with tree block size <
PAGE_SIZE") changed FS_IOC_ENABLE_VERITY to use __kernel_read() to read
th
fsverity: reject FS_IOC_ENABLE_VERITY on mode 3 fds
Commit 56124d6c87fd ("fsverity: support enabling with tree block size <
PAGE_SIZE") changed FS_IOC_ENABLE_VERITY to use __kernel_read() to read
the file's data, instead of direct pagecache accesses.
An unintended consequence of this is that the
'WARN_ON_ONCE(!(file->f_mode & FMODE_READ))' in __kernel_read() became
reachable by fuzz tests. This happens if FS_IOC_ENABLE_VERITY is called
on a fd opened with access mode 3, which means "ioctl access only".
Arguably, FS_IOC_ENABLE_VERITY should work on ioctl-only fds. But
ioctl-only fds are a weird Linux extension that is rarely used and that
few people even know about. (The documentation for FS_IOC_ENABLE_VERITY
even specifically says it requires O_RDONLY.) It's probably not
worthwhile to make the ioctl internally open a new fd just to handle
this case. Thus, just reject the ioctl on such fds for now.
Fixes: 56124d6c87fd ("fsverity: support enabling with tree block size < PAGE_SIZE")
Reported-by: syzbot+51177e4144d764827c45@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=2281afcbbfa8fdb92f9887479cc0e4180f1c6b28
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230406215106.235829-1-ebiggers@kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| 39049b69 | 27-Mar-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: explicitly check for buffer overflow in build_merkle_tree()
The new Merkle tree construction algorithm is a bit fragile in that it
may overflow the 'root_hash' array if the tree actually g
fsverity: explicitly check for buffer overflow in build_merkle_tree()
The new Merkle tree construction algorithm is a bit fragile in that it
may overflow the 'root_hash' array if the tree actually generated does
not match the calculated tree parameters.
This should never happen unless there is a filesystem bug that allows
the file size to change despite deny_write_access(), or a bug in the
Merkle tree logic itself. Regardless, it's fairly easy to check for
buffer overflow here, so let's do so.
This is a robustness improvement only; this case is not currently known
to be reachable. I've added a Fixes tag anyway, since I recommend that
this be included in kernels that have the mentioned commit.
Fixes: 56124d6c87fd ("fsverity: support enabling with tree block size < PAGE_SIZE")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230328041505.110162-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| 8eb8af4b | 27-Mar-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: use WARN_ON_ONCE instead of WARN_ON
As per Linus's suggestion
(https://lore.kernel.org/r/CAHk-=whefxRGyNGzCzG6BVeM=5vnvgb-XhSeFJVxJyAxAF8XRA@mail.gmail.com),
use WARN_ON_ONCE instead of WA
fsverity: use WARN_ON_ONCE instead of WARN_ON
As per Linus's suggestion
(https://lore.kernel.org/r/CAHk-=whefxRGyNGzCzG6BVeM=5vnvgb-XhSeFJVxJyAxAF8XRA@mail.gmail.com),
use WARN_ON_ONCE instead of WARN_ON. This barely adds any extra
overhead, and it makes it so that if any of these ever becomes reachable
(they shouldn't, but that's the point), the logs can't be flooded.
Link: https://lore.kernel.org/r/20230406181542.38894-1-ebiggers@kernel.org
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| a075bacd | 14-Mar-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: don't drop pagecache at end of FS_IOC_ENABLE_VERITY
The full pagecache drop at the end of FS_IOC_ENABLE_VERITY is causing
performance problems and is hindering adoption of fsverity. It wa
fsverity: don't drop pagecache at end of FS_IOC_ENABLE_VERITY
The full pagecache drop at the end of FS_IOC_ENABLE_VERITY is causing
performance problems and is hindering adoption of fsverity. It was
intended to solve a race condition where unverified pages might be left
in the pagecache. But actually it doesn't solve it fully.
Since the incomplete solution for this race condition has too much
performance impact for it to be worth it, let's remove it for now.
Fixes: 3fda4c617e84 ("fs-verity: implement FS_IOC_ENABLE_VERITY ioctl")
Cc: stable@vger.kernel.org
Reviewed-by: Victor Hsieh <victorhsieh@google.com>
Link: https://lore.kernel.org/r/20230314235332.50270-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
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| 5d0f0e57 | 27-Jan-2023 |
Eric Biggers <ebiggers@google.com> |
fsverity: support verifying data from large folios
Try to make fs/verity/verify.c aware of large folios. This includes
making fsverity_verify_bio() support the case where the bio contains
large fol
fsverity: support verifying data from large folios
Try to make fs/verity/verify.c aware of large folios. This includes
making fsverity_verify_bio() support the case where the bio contains
large folios, and adding a function fsverity_verify_folio() which is the
equivalent of fsverity_verify_page().
There's no way to actually test this with large folios yet, but I've
tested that this doesn't cause any regressions.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20230127221529.299560-1-ebiggers@kernel.org
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| 56124d6c | 23-Dec-2022 |
Eric Biggers <ebiggers@google.com> |
fsverity: support enabling with tree block size < PAGE_SIZE
Make FS_IOC_ENABLE_VERITY support values of
fsverity_enable_arg::block_size other than PAGE_SIZE.
To make this possible, rework build_mer
fsverity: support enabling with tree block size < PAGE_SIZE
Make FS_IOC_ENABLE_VERITY support values of
fsverity_enable_arg::block_size other than PAGE_SIZE.
To make this possible, rework build_merkle_tree(), which was reading
data and hash pages from the file and assuming that they were the same
thing as "blocks".
For reading the data blocks, just replace the direct pagecache access
with __kernel_read(), to naturally read one block at a time.
(A disadvantage of the above is that we lose the two optimizations of
hashing the pagecache pages in-place and forcing the maximum readahead.
That shouldn't be very important, though.)
The hash block reads are a bit more difficult to handle, as the only way
to do them is through fsverity_operations::read_merkle_tree_page().
Instead, let's switch to the single-pass tree construction algorithm
that fsverity-utils uses. This eliminates the need to read back any
hash blocks while the tree is being built, at the small cost of an extra
block-sized memory buffer per Merkle tree level. This is probably what
I should have done originally.
Taken together, the above two changes result in page-size independent
code that is also a bit simpler than what we had before.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20221223203638.41293-8-ebiggers@kernel.org
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| 5306892a | 23-Dec-2022 |
Eric Biggers <ebiggers@google.com> |
fsverity: support verification with tree block size < PAGE_SIZE
Add support for verifying data from verity files whose Merkle tree block
size is less than the page size. The main use case for this
fsverity: support verification with tree block size < PAGE_SIZE
Add support for verifying data from verity files whose Merkle tree block
size is less than the page size. The main use case for this is to allow
a single Merkle tree block size to be used across all systems, so that
only one set of fsverity file digests and signatures is needed.
To do this, eliminate various assumptions that the Merkle tree block
size and the page size are the same:
- Make fsverity_verify_page() a wrapper around a new function
fsverity_verify_blocks() which verifies one or more blocks in a page.
- When a Merkle tree block is needed, get the corresponding page and
only verify and use the needed portion. (The Merkle tree continues to
be read and cached in page-sized chunks; that doesn't need to change.)
- When the Merkle tree block size and page size differ, use a bitmap
fsverity_info::hash_block_verified to keep track of which Merkle tree
blocks have been verified, as PageChecked cannot be used directly.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20221223203638.41293-7-ebiggers@kernel.org
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| f45555bf | 23-Dec-2022 |
Eric Biggers <ebiggers@google.com> |
fsverity: replace fsverity_hash_page() with fsverity_hash_block()
In preparation for allowing the Merkle tree block size to differ from
PAGE_SIZE, replace fsverity_hash_page() with fsverity_hash_blo
fsverity: replace fsverity_hash_page() with fsverity_hash_block()
In preparation for allowing the Merkle tree block size to differ from
PAGE_SIZE, replace fsverity_hash_page() with fsverity_hash_block(). The
new function is similar to the old one, but it operates on the block at
the given offset in the page instead of on the full page.
(For now, all callers still pass a full page.)
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20221223203638.41293-6-ebiggers@kernel.org
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| 55eed69c | 23-Dec-2022 |
Eric Biggers <ebiggers@google.com> |
fsverity: use EFBIG for file too large to enable verity
Currently, there is an implementation limit where files can't have more
than 8 Merkle tree levels. With SHA-256 and 4K blocks, this limit is
fsverity: use EFBIG for file too large to enable verity
Currently, there is an implementation limit where files can't have more
than 8 Merkle tree levels. With SHA-256 and 4K blocks, this limit is
never reached, since a file would need to be larger than 2**64 bytes to
need 9 levels. However, with SHA-512, 9 levels are needed for files
larger than about 1.15 EB, which is possible on btrfs. Therefore, this
limit technically became reachable when btrfs added fsverity support.
Meanwhile, support for merkle_tree_block_size < PAGE_SIZE will introduce
another implementation limit on file size, resulting from the use of an
in-memory bitmap to track which Merkle tree blocks have been verified.
In any case, currently FS_IOC_ENABLE_VERITY fails with EINVAL when the
file is too large. This is undocumented, and also ambiguous since
EINVAL can mean other things too. Let's change the error code to EFBIG,
which is much clearer, and document it.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20221223203638.41293-5-ebiggers@kernel.org
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| 579a12f7 | 23-Dec-2022 |
Eric Biggers <ebiggers@google.com> |
fsverity: store log2(digest_size) precomputed
Add log_digestsize to struct merkle_tree_params so that it can be used
in verify.c. Also save memory by using u8 for all the log_* fields.
Signed-off-
fsverity: store log2(digest_size) precomputed
Add log_digestsize to struct merkle_tree_params so that it can be used
in verify.c. Also save memory by using u8 for all the log_* fields.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20221223203638.41293-4-ebiggers@kernel.org
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| 9098f36b | 23-Dec-2022 |
Eric Biggers <ebiggers@google.com> |
fsverity: simplify Merkle tree readahead size calculation
First, calculate max_ra_pages more efficiently by using the bio size.
Second, calculate the number of readahead pages from the hash page
in
fsverity: simplify Merkle tree readahead size calculation
First, calculate max_ra_pages more efficiently by using the bio size.
Second, calculate the number of readahead pages from the hash page
index, instead of calculating it ahead of time using the data page
index. This ends up being a bit simpler, especially since level 0 is
last in the tree, so we can just limit the readahead to the tree size.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20221223203638.41293-3-ebiggers@kernel.org
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| 284d5db5 | 23-Dec-2022 |
Eric Biggers <ebiggers@google.com> |
fsverity: use unsigned long for level_start
fs/verity/ isn't consistent with whether Merkle tree block indices are
'unsigned long' or 'u64'. There's no real point to using u64 for them,
though, sin
fsverity: use unsigned long for level_start
fs/verity/ isn't consistent with whether Merkle tree block indices are
'unsigned long' or 'u64'. There's no real point to using u64 for them,
though, since (a) a Merkle tree with over ULONG_MAX blocks would only be
needed for a file larger than MAX_LFS_FILESIZE, and (b) for reads, the
status of all Merkle tree blocks has to be tracked in memory.
Therefore, let's make things a bit more efficient on 32-bit systems by
using 'unsigned long[]' for merkle_tree_params::level_start, instead of
'u64[]'. Also, to be extra safe, explicitly check that there aren't
more than ULONG_MAX Merkle tree blocks.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20221223203638.41293-2-ebiggers@kernel.org
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