In the Linux kernel, the following vulnerability has been resolved:
hwmon: (powerz) Fix use-after-free on USB disconnect
After powerz_disconnect() frees the URB and releases the mutex, a
subsequent powerz_read() call can acquire the mutex and call
powerz_read_data(), which dereferences the freed URB pointer.
Fix by:
- Setting priv->urb to NULL in powerz_disconnect() so that
powerz_read_data() can detect the disconnected state.
- Adding a !priv->urb check at the start of powerz_read_data()
to return -ENODEV on a disconnected device.
- Moving usb_set_intfdata() before hwmon registration so the
disconnect handler can always find the priv pointer.
In the Linux kernel, the following vulnerability has been resolved:
s390/mm: Add missing secure storage access fixups for donated memory
There are special cases where secure storage access exceptions happen
in a kernel context for pages that don't have the PG_arch_1 bit
set. That bit is set for non-exported guest secure storage (memory)
but is absent on storage donated to the Ultravisor since the kernel
isn't allowed to export donated pages.
Prior to this patch we would try to export the page by calling
arch_make_folio_accessible() which would instantly return since the
arch bit is absent signifying that the page was already exported and
no further action is necessary. This leads to secure storage access
exception loops which can never be resolved.
With this patch we unconditionally try to export and if that fails we
fixup.
In the Linux kernel, the following vulnerability has been resolved:
spi: spi-dw-dma: fix print error log when wait finish transaction
If an error occurs, the device may not have a current message. In this
case, the system will crash.
In this case, it's better to use dev from the struct ctlr (struct spi_controller*).
In the Linux kernel, the following vulnerability has been resolved:
wifi: cfg80211: cancel pmsr_free_wk in cfg80211_pmsr_wdev_down
When the nl80211 socket that originated a PMSR request is
closed, cfg80211_release_pmsr() sets the request's nl_portid
to zero and schedules pmsr_free_wk to process the abort
asynchronously. If the interface is concurrently torn down
before that work runs, cfg80211_pmsr_wdev_down() calls
cfg80211_pmsr_process_abort() directly. However, the already-
scheduled pmsr_free_wk work item remains pending and may run
after the interface has been removed from the driver. This
could cause the driver's abort_pmsr callback to operate on a
torn-down interface, leading to undefined behavior and
potential crashes.
Cancel pmsr_free_wk synchronously in cfg80211_pmsr_wdev_down()
before calling cfg80211_pmsr_process_abort(). This ensures any
pending or in-progress work is drained before interface teardown
proceeds, preventing the work from invoking the driver abort
callback after the interface is gone.
In the Linux kernel, the following vulnerability has been resolved:
ipv4: nexthop: allocate skb dynamically in rtm_get_nexthop()
When querying a nexthop object via RTM_GETNEXTHOP, the kernel currently
allocates a fixed-size skb using NLMSG_GOODSIZE. While sufficient for
single nexthops and small Equal-Cost Multi-Path groups, this fixed
allocation fails for large nexthop groups like 512 nexthops.
This results in the following warning splat:
WARNING: net/ipv4/nexthop.c:3395 at rtm_get_nexthop+0x176/0x1c0, CPU#20: rep/4608
[...]
RIP: 0010:rtm_get_nexthop (net/ipv4/nexthop.c:3395)
[...]
Call Trace:
<TASK>
rtnetlink_rcv_msg (net/core/rtnetlink.c:6989)
netlink_rcv_skb (net/netlink/af_netlink.c:2550)
netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344)
netlink_sendmsg (net/netlink/af_netlink.c:1894)
____sys_sendmsg (net/socket.c:721 net/socket.c:736 net/socket.c:2585)
___sys_sendmsg (net/socket.c:2641)
__sys_sendmsg (net/socket.c:2671)
do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
</TASK>
Fix this by allocating the size dynamically using nh_nlmsg_size() and
using nlmsg_new(), this is consistent with nexthop_notify() behavior. In
addition, adjust nh_nlmsg_size_grp() so it calculates the size needed
based on flags passed. While at it, also add the size of NHA_FDB for
nexthop group size calculation as it was missing too.
This cannot be reproduced via iproute2 as the group size is currently
limited and the command fails as follows:
addattr_l ERROR: message exceeded bound of 1048
In the Linux kernel, the following vulnerability has been resolved:
can: raw: fix ro->uniq use-after-free in raw_rcv()
raw_release() unregisters raw CAN receive filters via can_rx_unregister(),
but receiver deletion is deferred with call_rcu(). This leaves a window
where raw_rcv() may still be running in an RCU read-side critical section
after raw_release() frees ro->uniq, leading to a use-after-free of the
percpu uniq storage.
Move free_percpu(ro->uniq) out of raw_release() and into a raw-specific
socket destructor. can_rx_unregister() takes an extra reference to the
socket and only drops it from the RCU callback, so freeing uniq from
sk_destruct ensures the percpu area is not released until the relevant
callbacks have drained.
[mkl: applied manually]
In the Linux kernel, the following vulnerability has been resolved:
driver core: platform: use generic driver_override infrastructure
When a driver is probed through __driver_attach(), the bus' match()
callback is called without the device lock held, thus accessing the
driver_override field without a lock, which can cause a UAF.
Fix this by using the driver-core driver_override infrastructure taking
care of proper locking internally.
Note that calling match() from __driver_attach() without the device lock
held is intentional. [1]
In the Linux kernel, the following vulnerability has been resolved:
xfrm: prevent policy_hthresh.work from racing with netns teardown
A XFRM_MSG_NEWSPDINFO request can queue the per-net work item
policy_hthresh.work onto the system workqueue.
The queued callback, xfrm_hash_rebuild(), retrieves the enclosing
struct net via container_of(). If the net namespace is torn down
before that work runs, the associated struct net may already have
been freed, and xfrm_hash_rebuild() may then dereference stale memory.
xfrm_policy_fini() already flushes policy_hash_work during teardown,
but it does not synchronize policy_hthresh.work.
Synchronize policy_hthresh.work in xfrm_policy_fini() as well, so the
queued work cannot outlive the net namespace teardown and access a
freed struct net.
In the Linux kernel, the following vulnerability has been resolved:
btrfs: set BTRFS_ROOT_ORPHAN_CLEANUP during subvol create
We have recently observed a number of subvolumes with broken dentries.
ls-ing the parent dir looks like:
drwxrwxrwt 1 root root 16 Jan 23 16:49 .
drwxr-xr-x 1 root root 24 Jan 23 16:48 ..
d????????? ? ? ? ? ? broken_subvol
and similarly stat-ing the file fails.
In this state, deleting the subvol fails with ENOENT, but attempting to
create a new file or subvol over it errors out with EEXIST and even
aborts the fs. Which leaves us a bit stuck.
dmesg contains a single notable error message reading:
"could not do orphan cleanup -2"
2 is ENOENT and the error comes from the failure handling path of
btrfs_orphan_cleanup(), with the stack leading back up to
btrfs_lookup().
btrfs_lookup
btrfs_lookup_dentry
btrfs_orphan_cleanup // prints that message and returns -ENOENT
After some detailed inspection of the internal state, it became clear
that:
- there are no orphan items for the subvol
- the subvol is otherwise healthy looking, it is not half-deleted or
anything, there is no drop progress, etc.
- the subvol was created a while ago and does the meaningful first
btrfs_orphan_cleanup() call that sets BTRFS_ROOT_ORPHAN_CLEANUP much
later.
- after btrfs_orphan_cleanup() fails, btrfs_lookup_dentry() returns -ENOENT,
which results in a negative dentry for the subvolume via
d_splice_alias(NULL, dentry), leading to the observed behavior. The
bug can be mitigated by dropping the dentry cache, at which point we
can successfully delete the subvolume if we want.
i.e.,
btrfs_lookup()
btrfs_lookup_dentry()
if (!sb_rdonly(inode->vfs_inode)->vfs_inode)
btrfs_orphan_cleanup(sub_root)
test_and_set_bit(BTRFS_ROOT_ORPHAN_CLEANUP)
btrfs_search_slot() // finds orphan item for inode N
...
prints "could not do orphan cleanup -2"
if (inode == ERR_PTR(-ENOENT))
inode = NULL;
return d_splice_alias(NULL, dentry) // NEGATIVE DENTRY for valid subvolume
btrfs_orphan_cleanup() does test_and_set_bit(BTRFS_ROOT_ORPHAN_CLEANUP)
on the root when it runs, so it cannot run more than once on a given
root, so something else must run concurrently. However, the obvious
routes to deleting an orphan when nlinks goes to 0 should not be able to
run without first doing a lookup into the subvolume, which should run
btrfs_orphan_cleanup() and set the bit.
The final important observation is that create_subvol() calls
d_instantiate_new() but does not set BTRFS_ROOT_ORPHAN_CLEANUP, so if
the dentry cache gets dropped, the next lookup into the subvolume will
make a real call into btrfs_orphan_cleanup() for the first time. This
opens up the possibility of concurrently deleting the inode/orphan items
but most typical evict() paths will be holding a reference on the parent
dentry (child dentry holds parent->d_lockref.count via dget in
d_alloc(), released in __dentry_kill()) and prevent the parent from
being removed from the dentry cache.
The one exception is delayed iputs. Ordered extent creation calls
igrab() on the inode. If the file is unlinked and closed while those
refs are held, iput() in __dentry_kill() decrements i_count but does
not trigger eviction (i_count > 0). The child dentry is freed and the
subvol dentry's d_lockref.count drops to 0, making it evictable while
the inode is still alive.
Since there are two races (the race between writeback and unlink and
the race between lookup and delayed iputs), and there are too many moving
parts, the following three diagrams show the complete picture.
(Only the second and third are races)
Phase 1:
Create Subvol in dentry cache without BTRFS_ROOT_ORPHAN_CLEANUP set
btrfs_mksubvol()
lookup_one_len()
__lookup_slow()
d_alloc_parallel()
__d_alloc() // d_lockref.count = 1
create_subvol(dentry)
// doesn't touch the bit..
d_instantiate_new(dentry, inode) // dentry in cache with d_lockref.c
---truncated---