Writing to the netdevsim debugfs file
"netdevsim/netdevsimN/fib/nexthop_bucket_activity" enters
nsim_nexthop_bucket_activity_write(), which looks up a nexthop in
data->nexthop_ht under rtnl_lock(). If a network namespace teardown,
devlink reload or device deletion runs concurrently, nsim_fib_destroy()
frees that rhashtable (and the surrounding nsim_fib_data) while the
write is still in flight, leading to a slab-use-after-free:

  BUG: KASAN: slab-use-after-free in nsim_nexthop_bucket_activity_write+0xb9e/0xdf0
  Read of size 4 at addr ff1100001a379808 by task syz.0.11967/27894

  CPU: 0 UID: 0 PID: 27894 Comm: syz.0.11967 Not tainted 7.1.0-rc4-gf6f1bfc1980a #4
  Call Trace:
   nsim_nexthop_bucket_activity_write+0xb9e/0xdf0
   full_proxy_write+0x135/0x1a0
   vfs_write+0x2e2/0x1040
   ksys_write+0x146/0x270
   __x64_sys_write+0x76/0xb0
   do_syscall_64+0xb9/0x5b0
   entry_SYSCALL_64_after_hwframe+0x74/0x7c

  Allocated by task 15957:
   rhashtable_init_noprof+0x3ec/0x860
   nsim_fib_create+0x371/0xca0
   nsim_drv_probe+0xd60/0x15c0
   ...
   new_device_store+0x425/0x7f0

  Freed by task 24:
   rhashtable_free_and_destroy+0x10d/0x620
   nsim_fib_destroy+0xc9/0x1c0
   nsim_dev_reload_destroy+0x1e7/0x530
   nsim_dev_reload_down+0x6b/0xd0
   devlink_reload+0x1b5/0x770
   devlink_pernet_pre_exit+0x25d/0x3a0
   ops_undo_list+0x1b7/0xb90
   cleanup_net+0x47f/0x8a0

  The buggy address belongs to the object at ff1100001a379800
   which belongs to the cache kmalloc-1k of size 1024

The freed 1k object is the bucket table of data->nexthop_ht. Shortly
after, the dangling table is dereferenced again and the machine also
takes a GPF in __rht_bucket_nested() from the same call site.

The root cause is a lifetime mismatch: the debugfs files reference
nsim_fib_data (the writer dereferences data->nexthop_ht), but the
interface is not bracketed around the lifetime of that data.
nsim_fib_destroy() freed both rhashtables and only removed the debugfs
directory afterwards, and nsim_fib_create() created the debugfs files
before the rhashtables were initialized and, on the error path, freed
them before removing the files. debugfs keeps the file itself alive
across a ->write() via debugfs_file_get()/debugfs_file_put()
(fs/debugfs/file.c), but it does not keep data->nexthop_ht alive, so the
in-flight writer dereferenced freed memory. rtnl_lock() in the writer
does not help, because the teardown path does not take rtnl around
rhashtable_free_and_destroy().

Fix it by bracketing the debugfs interface around the data it exposes,
keeping nsim_fib_create() and nsim_fib_destroy() symmetric:

 - In nsim_fib_destroy(), tear down the debugfs files before the data
   structures they reference. debugfs_remove_recursive() drops the
   initial active-user reference and then waits for every in-flight
   ->write() to drop its reference before returning, and rejects new
   opens (__debugfs_file_removed(), fs/debugfs/inode.c). Once it returns,
   no debugfs accessor can reach the FIB data, so the rhashtables and
   nsim_fib_data can be destroyed safely. This also covers the bool knobs
   in the same directory, which store pointers into the same
   nsim_fib_data, and the final kfree(data).

 - In nsim_fib_create(), create the debugfs files after the rhashtables
   and notifiers are set up. This closes the same race on the
   error-unwind path, where a concurrent writer could otherwise observe a
   half-constructed instance or a table that the unwind has already
   freed. (With only the destroy-side change, a writer racing the create
   window instead dereferences an uninitialized data->nexthop_ht.)

This is reproducible by racing, in a loop, writes to
/sys/kernel/debug/netdevsim/netdevsimN/fib/nexthop_bucket_activity
against a teardown of the same netdevsim instance -- a devlink reload
("devlink dev reload netdevsim/netdevsimN"), destroying the network
namespace it lives in, or "echo N > /sys/bus/netdevsim/del_device". It
was found with syzkaller; a syzkaller reproducer is available. A
standalone C reproducer does not trigger it reliably because the race
needs the netns-teardown/reload path.

Cc: <stable+noautosel@kernel.org> # netdevsim is a test harness, it's never loaded on production systems
Signed-off-by: Zijing Yin <yzjaurora@gmail.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260529135718.1804031-1-yzjaurora@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

This was done entirely with mindless brute force, using

    git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
        xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'

to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.

Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.

For the same reason the 'flex' versions will be done as a separate
conversion.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:

Single allocations:	kmalloc(sizeof(TYPE), ...)
are replaced with:	kmalloc_obj(TYPE, ...)

Array allocations:	kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with:	kmalloc_objs(TYPE, COUNT, ...)

Flex array allocations:	kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with:	kmalloc_flex(*PTR, FAM, COUNT, ...)

(where TYPE may also be *VAR)

The resulting allocations no longer return "void *", instead returning
"TYPE *".

Signed-off-by: Kees Cook <kees@kernel.org>

This was found by a static analyzer.
We should not forget the trailing zero after copy_from_user()
if we will further do some string operations, sscanf() in this
case. Adding a trailing zero will ensure that the function
performs properly.

Fixes: c6385c0b67c5 ("netdevsim: Allow reporting activity on nexthop buckets")
Signed-off-by: Zichen Xie <zichenxie0106@gmail.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20241022171907.8606-1-zichenxie0106@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

no_llseek had been defined to NULL two years ago, in commit 868941b14441
("fs: remove no_llseek")

To quote that commit,

  At -rc1 we'll need do a mechanical removal of no_llseek -

  git grep -l -w no_llseek | grep -v porting.rst | while read i; do
	sed -i '/\<no_llseek\>/d' $i
  done

  would do it.

Unfortunately, that hadn't been done.  Linus, could you do that now, so
that we could finally put that thing to rest? All instances are of the
form
	.llseek = no_llseek,
so it's obviously safe.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Conflicts:

net/ax25/af_ax25.c
  d7c4c9e075f8c ("ax25: fix incorrect dev_tracker usage")
  d62607c3fe459 ("net: rename reference+tracking helpers")

drivers/net/netdevsim/fib.c
  180a6a3ee60a ("netdevsim: fib: Fix reference count leak on route deletion failure")
  012ec02ae441 ("netdevsim: convert driver to use unlocked devlink API during init/fini")

Signed-off-by: Paolo Abeni <pabeni@redhat.com>

The previous patch ("netdevsim: fib: Fix reference count leak on route
deletion failure") fixed a reference count leak that happens on route
deletion failure.

Such failures can only be simulated by injecting slab allocation
failures, which cannot be surgically injected.

In order to be able to specifically test this scenario, add a debugfs
knob that allows user space to fail route deletion requests when
enabled.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

As part of FIB offload simulation, netdevsim stores IPv4 and IPv6 routes
and holds a reference on FIB info structures that in turn hold a
reference on the associated nexthop device(s).

In the unlikely case where we are unable to allocate memory to process a
route deletion request, netdevsim will not release the reference from
the associated FIB info structure, thereby preventing the associated
nexthop device(s) from ever being removed [1].

Fix this by scheduling a work item that will flush netdevsim's FIB table
upon route deletion failure. This will cause netdevsim to release its
reference from all the FIB info structures in its table.

Reported by Lucas Leong of Trend Micro Zero Day Initiative.

Fixes: 0ae3eb7b4611 ("netdevsim: fib: Perform the route programming in a non-atomic context")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Prepare for devlink reload being called with devlink->lock held and
convert the netdevsim driver to use unlocked devlink API during init and
fini flows. Take devl_lock() in reload_down() and reload_up() ops in the
meantime before reload cmd is converted to take the lock itself.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Use the new dscp_t type to replace the tos field of struct
nsim_fib4_rt. This ensures ECN bits are ignored and makes it compatible
with the dscp fields of struct fib_entry_notifier_info and struct
fib_rt_info.

This also allows sparse to flag potential incorrect uses of DSCP and
ECN bits.

Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>