| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: reject out-of-range nseconds in NFSv3 SETATTR and create ops
A client can send an NFSv3 SETATTR, CREATE, MKDIR, SYMLINK or MKNOD
carrying an atime or mtime whose nseconds field is out of range. The
value is well-formed on the wire and decodes cleanly into a valid
uint32, but it is not a valid timespec64: tv_nsec must be less than
NSEC_PER_SEC.
Nothing in the setattr path clamps it. notify_change() runs the time
through timestamp_truncate(), which does not reduce tv_nsec below
NSEC_PER_SEC when the filesystem supports nanosecond granularity
(s_time_gran == 1), and the inode atime/mtime setters store it verbatim
(only ctime is normalized, via inode_set_ctime_to_ts()). The
un-normalized value then corrupts on-disk metadata: ext4's
ext4_encode_extra_time() shifts tv_nsec left by EXT4_EPOCH_BITS, which
overflows the 32-bit extra field and clobbers the seconds-epoch bits, so
the stored seconds (and thus the year) are wrong on read-back. XFS with
bigtime mis-stores the timestamp for the same reason.
Validate the client-supplied atime/mtime in the proc handlers and return
NFS3ERR_INVAL before anything is changed. RFC 1813 lists NFS3ERR_INVAL
for SETATTR and describes it as the error for a value the server 'can
not store ... in its own representation'; the client maps it to EINVAL.
Checking in the proc handlers, rather than in nfsd_setattr(), keeps the
rejection in front of object creation. The create operations create the
object before nfsd_create_setattr() runs, so a late failure would leave
the new object behind and turn a non-idempotent request into a namespace
change that reports failure. The check is therefore done up front, for
the create operations before the object is created.
tv_nsec is a long, so the comparison casts it to unsigned long (the same
width) rather than to u32, matching timespec64_valid(). A u32 cast would
truncate on 64-bit; the unsigned long cast also rejects a value that
became negative when an out-of-range u32 wire nseconds was assigned to a
32-bit long.
Only client-supplied times are checked: SET_TO_SERVER_TIME requests
carry no client value. The sattrguard3 ctime is deliberately left alone:
an out-of-range guard simply never matches the object's ctime and yields
NFS3ERR_NOT_SYNC via the existing guardtime comparison, which is the
protocol-correct outcome rather than rejecting the request. |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: gate nfs2 setacl by argp->mask
The NFSACL v2 SETACL path shares the decoder convention used by its
v3 sibling: nfsaclsvc_decode_setaclargs() fills in argp->acl_access
only when NFS_ACL is set in the request mask and argp->acl_default
only when NFS_DFACL is set, leaving the other pointer NULL because
the argument buffer is zeroed up to pc_argzero before decode.
nfsacld_proc_setacl() then hands both pointers to set_posix_acl()
unconditionally. set_posix_acl(idmap, dentry, type, NULL) is the VFS
"remove this ACL type" operation, so an omitted arm is
indistinguishable from an explicit request to delete that ACL. A
SETACL carrying only NFS_ACL silently strips the directory's default
ACL; mask=0 strips both.
This is the same defect just fixed in nfsd3_proc_setacl(); apply the
same remedy. Gate each set_posix_acl() call on its mask bit and
initialize error to 0 so that a request with neither bit set leaves
the on-disk ACLs untouched and returns success. The out_drop_lock
path and the unconditional posix_acl_release() in
nfsaclsvc_release_setacl() already tolerate the skipped arms. |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()
dentry_create() can hypothetically provide a different dentry than the
one passed in. This could happen, for example, if the exported
filesystem is NFS, and the server returned to OPEN a filehandle which
matched a directory that was already in the dcache. Clearly this would
not be expected!
If this were to happen the dentry (child) that was already stored in
resfhp could be freed and later dereferenced.
We shouldn't call fh_compose() until we are certain that we have the
final dentry, so this patch moved the fh_compose() call to two places:
one for the case where the target already exists, and one after
dentry_create() where it was created. |
| In the Linux kernel, the following vulnerability has been resolved:
usb: dwc3: gadget: Fix use-after-free in dwc3_gadget_free_endpoints due to race condition
In dwc3_gadget_init_endpoint, &dep->nostream_work is bound with
dwc3_nostream_work, and dwc3_gadget_endpoint_stream_event can queue
this delayed work on system_percpu_wq when a DEPEVT_STREAM_NOSTREAM
event is received.
If we remove the gadget, dwc3_gadget_free_endpoints makes cleanup and
the memory allocated for dep with kzalloc() is released by kfree(dep),
while the delayed work mentioned above may still be pending or
running. The sequence of operations that may lead to a UAF bug is as
follows:
CPU0 CPU1
| dwc3_thread_interrupt
| dwc3_endpoint_interrupt
| dwc3_gadget_endpoint_stream_event
| queue_delayed_work(system_percpu_wq,
| &dep->nostream_work)
dwc3_gadget_free_endpoints |
dwc3_free_trb_pool(dep) |
list_del(&dep->endpoint.ep_list) |
dwc3_debugfs_remove_endpoint_dir(dep) |
kfree(dep) |
// dep is freed |
| dwc3_nostream_work
| // use dep (use-after-free)
Fix it by canceling the delayed work before kfree(dep) in
dwc3_gadget_free_endpoints. |
| In the Linux kernel, the following vulnerability has been resolved:
Revert "media: v4l2-dev: fix error handling in __video_register_device()"
This reverts commit 2a934fdb01db6458288fc9386d3d8ceba6dd551a.
The intentions of that patch were good, but it doesn't work.
The idea is that if device_register fails, you have to do a put_device
to let the ref counter release resources.
However, the V4L2 API says that if video_register_device() fails, then
you have to call video_device_release(), which kfree()s the video_device
struct.
But the put_device() will already have freed the struct, so you end
up in a double-free scenario.
There is not really a good way of fixing this without breaking
video_register_device() into two parts, one that initializes everything,
and one that does the actual device_register, and then converting all
V4L2 drivers to this new model.
That is a massive job, and it is very unlikely that device_register
will fail.
So rather than ending up in a double-free scenario, just revert this
patch, and in that case we'll have a small memory leak. Which is a lot
more robust. |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: clear opcnt on compound arg release to prevent OOB read
nfsd4_release_compoundargs() resets args->ops to the inline iops[8]
array when the dynamically-allocated ops buffer is freed, but leaves
args->opcnt at its original value (which can be up to 200 for NFSv4.1+
compounds).
If rq_status_counter is stuck at an odd value (which can happen when
nfsd_dispatch() hits an error path after setting it odd), the RPC
status dumpit handler reads min(opcnt, 16) entries from args->ops[].
Since iops only has 8 elements and is the last field in struct
nfsd4_compoundargs, reading indices 8-15 accesses adjacent slab memory
and leaks it to userspace via netlink.
Zero opcnt unconditionally in nfsd4_release_compoundargs() so stale
compound metadata is never exposed through the status interface.
[ cel: Remove the kvfree_rcu_mightsleep() sleep from the exposure window ] |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref
When CONFIG_NFSD_V4_2_INTER_SSC is enabled, nfsd4_putfh() can return
success with fh_dentry and fh_export both NULL if fh_verify() returns
nfserr_stale and putfh->no_verify is true. The NFSD4_FH_FOREIGN flag
is set, but the compound dispatch loop only uses this flag to bypass
the nfserr_nofilehandle check -- it does not prevent subsequent ops
from running with a NULL fh_dentry.
A remote client can exploit this by crafting a COMPOUND that includes
an inter-SSC COPY (which causes check_if_stalefh_allowed() to set
no_verify=true on the saved PUTFH) with an additional op inserted
between the source PUTFH and SAVEFH. For example, SETATTR calls
fh_want_write() which dereferences fh_export->ex_path.mnt without
calling fh_verify() first, causing a NULL pointer dereference in the
nfsd kthread.
Fix this by gating the dispatch loop: when NFSD4_FH_FOREIGN is set
and fh_dentry is NULL, only OP_SAVEFH (needed for the inter-SSC flow)
and ops with ALLOWED_WITHOUT_FH (which don't need a resolved
filehandle) may proceed. All other ops receive nfserr_stale, per
RFC 7862 Section 15.2.3 which specifies that foreign filehandle
validation is deferred to the consuming operation and NFS4ERR_STALE
returned at that point. |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: validate sockaddr length per family in listener_set
nfsd_sock_nl_policy declares NFSD_A_SOCK_ADDR as a bare NLA_BINARY
attribute with no minimum length. A CAP_NET_ADMIN caller can send a
16-byte NFSD_A_SOCK_ADDR with sa_family=AF_INET6, causing a 12-byte
OOB read across three consumers (rpc_cmp_addr_port, svc_find_listener,
kernel_bind).
nfsd_nl_listener_set_doit() also parsed and validated each listener
entry inline in two separate loops, interleaved with mutating the
running listener configuration. The validation was duplicated, used an
open-coded "nla_len < sizeof(struct sockaddr)" check that was too short
for AF_INET6, and handled a malformed entry inconsistently depending on
which loop noticed it.
Add an nfsd_nl_validate_listeners() helper that walks the entire list
once and confirms each entry parses, carries both an address and a
transport name, and is long enough for its address family
(sizeof(struct sockaddr_in) for AF_INET, sizeof(struct sockaddr_in6)
for AF_INET6, -EAFNOSUPPORT otherwise). Call it before taking
nfsd_mutex or creating the serv, so a malformed request fails cleanly
with no side effects.
Since every entry is known valid by the time the two existing loops
run, drop the redundant presence and per-family length checks from
both, leaving only the nla_parse_nested() call needed to extract the
data. |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: release path refs on follow_down() error
nfsd_cross_mnt() initializes a local struct path with mntget() and
dget() before calling follow_down(). On a negative return the error
arm jumps to out without releasing those references:
err = follow_down(&path, follow_flags);
if (err < 0)
goto out;
follow_down() never drops the caller's entry-time refs on any error
sub-case; for example a pre-cross d_manage() failure leaves path
untouched, so the mntget()/dget() taken on entry survive the call.
Every other early-exit arm in nfsd_cross_mnt() (other-namespace
return, IS_ERR(exp2), and the success tail after the swap) already
calls path_put(&path); the err < 0 arm is the lone omission. The
leak inflates mnt_count and d_count on each failed cross-mount,
blocking umount and pinning dentries against the shrinker, and is
reachable by any authenticated NFS client through nfsd_lookup_dentry
or the NFSv4 READDIR encode path.
Fix by calling path_put(&path) before the goto out in the err < 0
arm so the entry-time refs are released on all follow_down() error
returns. |
| In the Linux kernel, the following vulnerability has been resolved:
NFSD: check truncate permission under inode lock
nfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC
before it takes inode_lock(). The comparison uses the file size sampled
by that unlocked read, but the actual ATTR_SIZE update is applied later
under inode_lock() by notify_change().
This leaves a TOCTOU window for append-only files. If a client sends a
SETATTR that does not shrink the file at the time of the unlocked
sample, a concurrent append can extend the file before nfsd_setattr()
takes inode_lock(). notify_change() then applies a real truncation
without the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS
truncate syscall paths perform their own append-only checks before
calling notify_change(), so NFSD must make this decision against the
locked size it is about to change.
Split the write-count acquisition from the truncation permission check.
Keep get_write_access() before the locked setattr work, then recheck
whether the requested size is below i_size_read(inode) after inode_lock()
has been acquired and before notify_change(ATTR_SIZE). This also avoids
the plain unlocked inode->i_size load. |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: GICv2: Don't WARN on out-of-range GICV_DIR INTID
vgic_v2_deactivate() passes the INTID a guest wrote to GICV_DIR straight
to vgic_get_vcpu_irq(), and treats a failed lookup as a "can't happen"
condition with WARN_ON_ONCE().
The guest can make it happen at will, though: for any INTID outside of
the implemented SGI, PPI and SPI ranges the lookup returns NULL, since
GICv2 has no LPIs. A guest running with EOImode==1 writing such an INTID
to GICV_DIR triggers the WARN, and panics hosts running with
panic_on_warn.
Drop the WARN and ignore failed lookups. |
| In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: midi2: remove default configfs groups on teardown
f_midi2_alloc_inst() creates default configfs child groups for the
default endpoint and default block using configfs_add_default_group(),
setting their internal refcount to 1.
However, during function teardown in f_midi2_free_inst() or EP cleanup
in f_midi2_ep_opts_release(), configfs_remove_default_groups() is
never called, therefore never dropping the refcount and leaking struct
f_midi2_ep_opts and f_midi2_block_opts.
Add the missing configfs_remove_default_groups() in the afformentioned
functions to free the structs properly. |
| In the Linux kernel, the following vulnerability has been resolved:
debugfs: Fix lockdown check for mmap_prepare
Commit 651fdda8406d ("relay: update relay to use mmap_prepare")
changed the `mmap` file operation to `mmap_prepare` for relayfs, but
the lockdown check in debugfs was not updated accordingly.
This prevents debugfs from being locked down when the kernel is in
integrity mode if a file uses `mmap_prepare` but not `mmap`.
Since the conversion to `mmap_prepare` across the kernel is not yet
complete, update the lockdown check to look for both `mmap` and
`mmap_prepare` to ensure comprehensive coverage. |
| In the Linux kernel, the following vulnerability has been resolved:
mm/kmemleak: avoid soft lockup when scanning task stacks
Patch series "mm/kmemleak: avoid soft lockup when scanning task", v3.
kmemleak_scan() scans every task stack under one rcu_read_lock() with no
reschedule point, which can trip the soft lockup watchdog on hosts with
very many threads.
That prints the following message, depending on the workload+host
configuration:
watchdog: BUG: soft lockup - CPU#35 stuck for 22s! [kmemleak:537]
scan_block
kmemleak_scan
kmemleak_scan_thread
kthread
Patch 1 walks the tasks with find_ge_pid() so the scan reschedules between
tasks
Patches 2-3 let the scan loops stop early once a scan is interrupted.
This patch (of 3):
kmemleak_scan() walks every thread and scans its kernel stack under a
single rcu_read_lock() with no reschedule point. On a host with very many
threads -- amplified by KASAN/lockdep in debug builds -- this loop can hog
a CPU long enough to trip the soft lockup watchdog:
watchdog: BUG: soft lockup - CPU#35 stuck for 22s! [kmemleak:537]
scan_block
kmemleak_scan
kmemleak_scan_thread
kthread
A cond_resched() cannot be added directly: the loop runs inside an RCU
read-side critical section.
Walk the tasks one PID at a time with find_ge_pid(), taking the RCU read
lock only to look up and pin each task. The stack is then scanned with no
lock held, so cond_resched() runs between tasks and the scan stops early
on scan_should_stop(). This follows the next_tgid()/task_seq_get_next()
iteration pattern and keeps each RCU critical section short. |
| In the Linux kernel, the following vulnerability has been resolved:
apparmor: fix cred UAF caused by begin_current_label_crit_section()
AppArmor's begin_current_label_crit_section() is a scary function called
from lots of LSM hooks (in particular VFS/socket-related ones) that checks
if the label referenced by the current creds is marked FLAG_STALE, and if
so, attempts to use aa_replace_current_label() to replace the creds with an
updated version that uses a new label.
The first problem with this is that it would directly lead to UAF of
`struct cred` if anything in the kernel takes a pointer to the current
creds and accesses these past a security hook invocation that replaces
creds, like so:
```
const struct cred *cred = current_cred();
alloc_file_pseudo(...);
uid_t uid = cred->euid;
```
I don't know if anything in the kernel actually does this, but I think it
is very surprising that this pattern could lead to UAF.
The second problem is that things go wrong when aa_replace_current_label()
runs with overridden credentials. aa_replace_current_label() bails out if
`current_cred() != current_real_cred()` (mirroring the check in
proc_pid_attr_write()), but this check can't actually reliably detect
overridden credentials because the overridden creds can be the same as the
objective creds.
So in approximately the following scenario, things go wrong:
1. task begins with <creds A> (as both objective and subjective creds),
with refcount=2
2. task grabs an extra reference on <creds A> for overriding
3. task calls override_creds(<creds A>), which returns a pointer to the old
subjective creds (<creds A>)
4. task enters AppArmor LSM hook
5. AppArmor checks that objective/subjective creds are equal
6. AppArmor replaces both cred pointers with <creds B> and drops 2 refs on
<creds A>
7. task leaves AppArmor LSM hook
8. task calls revert_creds(<creds A>)
9. now task->cred is <creds A> while task->real_cred is <creds B>, but the
task_struct logically holds two references to <creds B>
10. another task drops the extra reference on <creds A> that was used for
overriding, refcount drops to 0
11. now task->real_cred points to freed creds
At this point, any access to current_cred() will be UAF.
I have a test case where I run aa-disable on a profile while a process
using that profile is blocked on splice() from a FUSE passthrough file into
a full pipe; after the profile update, the pipe becomes empty, splice()
resumes, the credentials go out of sync, and a subsequent getuid() syscall
results in a KASAN UAF splat.
To fix this, instead of directly replacing creds, do it via task_work that
will run at the end of the current syscall. (The point in time at which the
cred replacement happens should have no correctness impact; it is just a
performance optimization to avoid unnecessarily touching the refcount of
the new label.)
Note that AppArmor still performs direct cred replacements in the
sb_pivotroot LSM hook after this change, and that direct cred replacements
can still happen in VFS ->write() callbacks via proc_pid_attr_write().
There are two options for what to do with aa_dup_task_ctx(): Either
explicitly reset new->label_replacement_pending after the entire
aa_task_ctx has been copied, or switch to manually copying members over.
I am switching to manually copying members over because that should make
bugs more obvious. |
| In the Linux kernel, the following vulnerability has been resolved:
rust: devres: fix race between concurrent revokers
There is a potential race condition when two paths try to revoke a
Devres concurrently.
The driver core's devres_release_all() calls Revocable::revoke() via the
release callback, while Devres::drop() calls revoke_nosync() on another
CPU.
The revoker that does not claim the is_available swap returns
immediately, but the revoker that did may still be executing
drop_in_place() on the inner data. This can cause a use-after-free when
the other revoker's caller proceeds to drop adjacent resources that
drop_in_place() still references (e.g., Devres<DmaMappedSgt> racing with
SGTable freeing the backing sg_table and pages).
Fix this by adding a Completion. The release callback signals the
Completion after revoke() finishes, and Devres::drop() waits for it when
it loses the is_available swap. This ensures the wrapped object is fully
torn down before Devres::drop() returns. |
| In the Linux kernel, the following vulnerability has been resolved:
ovl: fix double end_creating() on the casefold-mismatch path
ovl_create_real() releases the new dentry twice when the casefold
consistency check fails. The S_IFDIR branch calls end_creating() and
sets err, then falls through to the common out: label which calls
end_creating() on the same dentry again:
case S_IFDIR:
newdentry = ovl_do_mkdir(ofs, dir, newdentry, attr->mode);
err = PTR_ERR_OR_ZERO(newdentry);
if (!err && ofs->casefold != ovl_dentry_casefolded(newdentry)) {
pr_warn_ratelimited(...);
end_creating(newdentry); /* first */
err = -EINVAL;
}
break;
...
if (err)
goto out;
...
out:
if (err) {
end_creating(newdentry); /* second, same dentry */
return ERR_PTR(err);
}
end_creating() is end_dirop(), which does inode_unlock() on the parent
and dput() on the dentry, so the parent directory's i_rwsem is unlocked
twice and the dentry is put twice. The second unlock releases a lock
that is not held, which is what wedges every later creation under that
parent, and the second dput() drops a reference that was never taken.
The branch was added by commit dfc7da402ccc ("ovl: Check for casefold
consistency when creating new dentries") as a bare dput(), which already
released the reference twice; commit fe497f0759e0 ("VFS: change
vfs_mkdir() to unlock on failure.") converted both sites to
end_creating(), adding the double unlock.
This is reachable by an unprivileged user. The casefold consistency of
the layers is validated at mount time in ovl_parse_layer(), and again on
every lookup in ovl_lookup_single(), but ofs->workdir is the internal
"work" subdirectory created inside the user-supplied workdir, and that
subdirectory is not re-checked. Marking it casefolded after the mount
therefore makes every ovl_create_temp() inherit the wrong state - and
that path reaches ovl_create_real() through ovl_start_creating_temp(),
which uses start_creating() with a generated name and so never runs the
lookup-time check.
unshare -Urm
mount -t tmpfs -o casefold=utf8-12.1.0 tmpfs mnt
mkdir -p mnt/lower/d mnt/upper mnt/work mnt/merged
mount -t overlay ovl -o lowerdir=mnt/lower,\
upperdir=mnt/upper,workdir=mnt/work mnt/merged
chattr +F mnt/work/work
mkdir mnt/merged/d/sub # directory copy-up
overlayfs: wrong inherited casefold (work/#5)
and the next copy-up blocks forever on the parent's i_rwsem:
mkdir D start_creating+0x65/0xb0
ovl_start_creating_temp+0xb0/0xe0 [overlay]
ovl_create_temp+0xa3/0x1d0 [overlay]
ovl_copy_up_one+0x1f1c/0x21c0 [overlay]
ovl_copy_up_flags+0xf5/0x140 [overlay]
ovl_create_object+0xb7/0x220 [overlay]
ovl_mkdir+0x23/0x40 [overlay]
Drop the end_creating() from the branch and let out: own the cleanup,
which is what every other error path in this function already does. |
| In the Linux kernel, the following vulnerability has been resolved:
hsi: omap_ssi_core: fix missing DMA mask setup for SSI controller device
The OMAP SSI driver uses a synthetic HSI controller device allocated via
hsi_alloc_controller(), which does not go through the normal OF/platform
device initialization path.
As a result, the embedded struct device does not have a DMA mask
initialized by default.
After recent DMA API hardening changes, dma_map_sg() and related helpers
now require a valid dma_mask to be present, otherwise the driver may
crash or trigger warnings when attempting DMA mapping operations.
Fix this by explicitly initializing the DMA mask for the SSI controller
device and setting a 32-bit DMA mask, which matches the hardware
capabilities. |
| In the Linux kernel, the following vulnerability has been resolved:
ecryptfs: reject oversized encrypted_key_size in parse_tag_3_packet
parse_tag_3_packet() set encrypted_key_size from the Tag 3 packet body
without bounding it against ECRYPTFS_MAX_KEY_BYTES (64). When
encrypted_key_size > 64, decrypt_passphrase_encrypted_session_key()
sets decrypted_key_size = encrypted_key_size and performs two
out-of-bounds writes:
1. crypto_skcipher_decrypt() writes encrypted_key_size bytes into
decrypted_key[64] via scatterlist, overflowing into the parent
ecryptfs_auth_tok struct.
2. memcpy(crypt_stat->key, decrypted_key, decrypted_key_size) writes
into crypt_stat->key[64], corrupting root_iv, keysig_list, and
mutexes in ecryptfs_crypt_stat.
Only AES-192 (cipher code 0x08) enables this because it sets
crypt_stat->key_size = 24 independently of encrypted_key_size,
allowing crypto_skcipher_setkey() to succeed while encrypted_key_size
exceeds ECRYPTFS_MAX_KEY_BYTES.
The PKI decryption path (parse_tag_65_packet) already validates
decrypted_key_size <= ECRYPTFS_MAX_KEY_BYTES; the passphrase path
omits this check.
Bound encrypted_key_size against ECRYPTFS_MAX_KEY_BYTES (64) rather
than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES (512). The 64-byte limit also
protects the 512-byte encrypted_key[] buffer, so the former 512-byte
check is removed as redundant.
[tyhicks: Adjust the code comment to refer to macros representing the
buffer sizes rather than mentioning the buffer size values since they
may change in the future] |
| In the Linux kernel, the following vulnerability has been resolved:
fs/ntfs3: fix info-leak on partial LZNT decompress in ni_read_frame()
ni_read_frame() decompresses an LZNT $DATA frame into the vmapped target
pages and then trusts decompress_lznt()'s return value:
unc_size = decompress_lznt(frame_ondisk, ondisk_size, frame_mem,
frame_size);
if ((ssize_t)unc_size < 0) err = unc_size;
else if (!unc_size || unc_size > frame_size) err = -EINVAL;
decompress_lznt() stops as soon as the compressed stream is exhausted
(e.g. a zero chunk header) and returns the number of bytes it actually
wrote, which may be far less than frame_size. The bytes between unc_size
and frame_size are never written. The only memset() that follows zeroes
the region beyond i_valid; when the frame lies entirely within the file's
valid size that memset() does not run, so the gap retains whatever was in
the just-vmapped pages. All pages are then marked uptodate and returned
to userspace, disclosing uninitialized (recently-freed) kernel page
memory. A crafted compressed file whose stream decompresses to only a few
bytes leaks the remainder of every frame on a plain read(2), which is
enough to recover kernel pointers and defeat KASLR.
Zero the [unc_size, frame_size) tail immediately after a successful LZNT
decompress so the remainder reads back as zero. |
