Linux: >> Linux Kernel >> 5.15.193 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
x86-64: rename misleadingly named '__copy_user_nocache()' function
This function was a masterclass in bad naming, for various historical
reasons.
It claimed to be a non-cached user copy. It is literally _neither_ of
those things. It's a specialty memory copy routine that uses
non-temporal stores for the destination (but not the source), and that
does exception handling for both source and destination accesses.
Also note that while it works for unaligned targets, any unaligned parts
(whether at beginning or end) will not use non-temporal stores, since
only words and quadwords can be non-temporal on x86.
The exception handling means that it _can_ be used for user space
accesses, but not on its own - it needs all the normal "start user space
access" logic around it.
But typically the user space access would be the source, not the
non-temporal destination. That was the original intention of this,
where the destination was some fragile persistent memory target that
needed non-temporal stores in order to catch machine check exceptions
synchronously and deal with them gracefully.
Thus that non-descriptive name: one use case was to copy from user space
into a non-cached kernel buffer. However, the existing users are a mix
of that intended use-case, and a couple of random drivers that just did
this as a performance tweak.
Some of those random drivers then actively misused the user copying
version (with STAC/CLAC and all) to do kernel copies without ever even
caring about the exception handling, _just_ for the non-temporal
destination.
Rename it as a first small step to actually make it halfway sane, and
change the prototype to be more normal: it doesn't take a user pointer
unless the caller has done the proper conversion, and the argument size
is the full size_t (it still won't actually copy more than 4GB in one
go, but there's also no reason to silently truncate the size argument in
the caller).
Finally, use this now sanely named function in the NTB code, which
mis-used a user copy version (with STAC/CLAC and all) of this interface
despite it not actually being a user copy at all.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-05
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nft_ct: drop pending enqueued packets on removal
Packets sitting in nfqueue might hold a reference to:
- templates that specify the conntrack zone, because a percpu area is
used and module removal is possible.
- conntrack timeout policies and helper, where object removal leave
a stale reference.
Since these objects can just go away, drop enqueued packets to avoid
stale reference to them.
If there is a need for finer grain removal, this logic can be revisited
to make selective packet drop upon dependencies.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-05-05
In the Linux kernel, the following vulnerability has been resolved:
serial: 8250: Fix TX deadlock when using DMA
`dmaengine_terminate_async` does not guarantee that the
`__dma_tx_complete` callback will run. The callback is currently the
only place where `dma->tx_running` gets cleared. If the transaction is
canceled and the callback never runs, then `dma->tx_running` will never
get cleared and we will never schedule new TX DMA transactions again.
This change makes it so we clear `dma->tx_running` after we terminate
the DMA transaction. This is "safe" because `serial8250_tx_dma_flush`
is holding the UART port lock. The first thing the callback does is also
grab the UART port lock, so access to `dma->tx_running` is serialized.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-05
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: L2CAP: Fix type confusion in l2cap_ecred_reconf_rsp()
l2cap_ecred_reconf_rsp() casts the incoming data to struct
l2cap_ecred_conn_rsp (the ECRED *connection* response, 8 bytes with
result at offset 6) instead of struct l2cap_ecred_reconf_rsp (2 bytes
with result at offset 0).
This causes two problems:
- The sizeof(*rsp) length check requires 8 bytes instead of the
correct 2, so valid L2CAP_ECRED_RECONF_RSP packets are rejected
with -EPROTO.
- rsp->result reads from offset 6 instead of offset 0, returning
wrong data when the packet is large enough to pass the check.
Fix by using the correct type. Also pass the already byte-swapped
result variable to BT_DBG instead of the raw __le16 field.
CVSS Score
7.1
EPSS Score
0.002
Published
2026-05-05
In the Linux kernel, the following vulnerability has been resolved:
dmaengine: idxd: Fix not releasing workqueue on .release()
The workqueue associated with an DSA/IAA device is not released when
the object is freed.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-05
In the Linux kernel, the following vulnerability has been resolved:
ext4: always drain queued discard work in ext4_mb_release()
While reviewing recent ext4 patch[1], Sashiko raised the following
concern[2]:
> If the filesystem is initially mounted with the discard option,
> deleting files will populate sbi->s_discard_list and queue
> s_discard_work. If it is then remounted with nodiscard, the
> EXT4_MOUNT_DISCARD flag is cleared, but the pending s_discard_work is
> neither cancelled nor flushed.
[1] https://lore.kernel.org/r/20260319094545.19291-1-qiang.zhang@linux.dev/
[2] https://sashiko.dev/#/patchset/20260319094545.19291-1-qiang.zhang%40linux.dev
The concern was valid, but it had nothing to do with the patch[1].
One of the problems with Sashiko in its current (early) form is that
it will detect pre-existing issues and report it as a problem with the
patch that it is reviewing.
In practice, it would be hard to hit deliberately (unless you are a
malicious syzkaller fuzzer), since it would involve mounting the file
system with -o discard, and then deleting a large number of files,
remounting the file system with -o nodiscard, and then immediately
unmounting the file system before the queued discard work has a change
to drain on its own.
Fix it because it's a real bug, and to avoid Sashiko from raising this
concern when analyzing future patches to mballoc.c.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-05
In the Linux kernel, the following vulnerability has been resolved:
ext4: fix iloc.bh leak in ext4_fc_replay_inode() error paths
During code review, Joseph found that ext4_fc_replay_inode() calls
ext4_get_fc_inode_loc() to get the inode location, which holds a
reference to iloc.bh that must be released via brelse().
However, several error paths jump to the 'out' label without
releasing iloc.bh:
- ext4_handle_dirty_metadata() failure
- sync_dirty_buffer() failure
- ext4_mark_inode_used() failure
- ext4_iget() failure
Fix this by introducing an 'out_brelse' label placed just before
the existing 'out' label to ensure iloc.bh is always released.
Additionally, make ext4_fc_replay_inode() propagate errors
properly instead of always returning 0.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-05
In the Linux kernel, the following vulnerability has been resolved:
media: vidtv: fix pass-by-value structs causing MSAN warnings
vidtv_ts_null_write_into() and vidtv_ts_pcr_write_into() take their
argument structs by value, causing MSAN to report uninit-value warnings.
While only vidtv_ts_null_write_into() has triggered a report so far,
both functions share the same issue.
Fix by passing both structs by const pointer instead, avoiding the
stack copy of the struct along with its MSAN shadow and origin metadata.
The functions do not modify the structs, which is enforced by the const
qualifier.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-02
In the Linux kernel, the following vulnerability has been resolved:
HID: multitouch: Check to ensure report responses match the request
It is possible for a malicious (or clumsy) device to respond to a
specific report's feature request using a completely different report
ID. This can cause confusion in the HID core resulting in nasty
side-effects such as OOB writes.
Add a check to ensure that the report ID in the response, matches the
one that was requested. If it doesn't, omit reporting the raw event and
return early.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-05-01
In the Linux kernel, the following vulnerability has been resolved:
HID: core: Mitigate potential OOB by removing bogus memset()
The memset() in hid_report_raw_event() has the good intention of
clearing out bogus data by zeroing the area from the end of the incoming
data string to the assumed end of the buffer. However, as we have
previously seen, doing so can easily result in OOB reads and writes in
the subsequent thread of execution.
The current suggestion from one of the HID maintainers is to remove the
memset() and simply return if the incoming event buffer size is not
large enough to fill the associated report.
Suggested-by Benjamin Tissoires <bentiss@kernel.org>
[bentiss: changed the return value]
CVSS Score
8.8
EPSS Score
0.002
Published
2026-05-01