In the Linux kernel, the following vulnerability has been resolved:
atm: lec: fix use-after-free in sock_def_readable()
A race condition exists between lec_atm_close() setting priv->lecd
to NULL and concurrent access to priv->lecd in send_to_lecd(),
lec_handle_bridge(), and lec_atm_send(). When the socket is freed
via RCU while another thread is still using it, a use-after-free
occurs in sock_def_readable() when accessing the socket's wait queue.
The root cause is that lec_atm_close() clears priv->lecd without
any synchronization, while callers dereference priv->lecd without
any protection against concurrent teardown.
Fix this by converting priv->lecd to an RCU-protected pointer:
- Mark priv->lecd as __rcu in lec.h
- Use rcu_assign_pointer() in lec_atm_close() and lecd_attach()
for safe pointer assignment
- Use rcu_access_pointer() for NULL checks that do not dereference
the pointer in lec_start_xmit(), lec_push(), send_to_lecd() and
lecd_attach()
- Use rcu_read_lock/rcu_dereference/rcu_read_unlock in send_to_lecd(),
lec_handle_bridge() and lec_atm_send() to safely access lecd
- Use rcu_assign_pointer() followed by synchronize_rcu() in
lec_atm_close() to ensure all readers have completed before
proceeding. This is safe since lec_atm_close() is called from
vcc_release() which holds lock_sock(), a sleeping lock.
- Remove the manual sk_receive_queue drain from lec_atm_close()
since vcc_destroy_socket() already drains it after lec_atm_close()
returns.
v2: Switch from spinlock + sock_hold/put approach to RCU to properly
fix the race. The v1 spinlock approach had two issues pointed out
by Eric Dumazet:
1. priv->lecd was still accessed directly after releasing the
lock instead of using a local copy.
2. The spinlock did not prevent packets being queued after
lec_atm_close() drains sk_receive_queue since timer and
workqueue paths bypass netif_stop_queue().
Note: Syzbot patch testing was attempted but the test VM terminated
unexpectedly with "Connection to localhost closed by remote host",
likely due to a QEMU AHCI emulation issue unrelated to this fix.
Compile testing with "make W=1 net/atm/lec.o" passes cleanly.
atm: lec: fix use-after-free in sock_def_readable()
A race condition exists between lec_atm_close() setting priv->lecd
to NULL and concurrent access to priv->lecd in send_to_lecd(),
lec_handle_bridge(), and lec_atm_send(). When the socket is freed
via RCU while another thread is still using it, a use-after-free
occurs in sock_def_readable() when accessing the socket's wait queue.
The root cause is that lec_atm_close() clears priv->lecd without
any synchronization, while callers dereference priv->lecd without
any protection against concurrent teardown.
Fix this by converting priv->lecd to an RCU-protected pointer:
- Mark priv->lecd as __rcu in lec.h
- Use rcu_assign_pointer() in lec_atm_close() and lecd_attach()
for safe pointer assignment
- Use rcu_access_pointer() for NULL checks that do not dereference
the pointer in lec_start_xmit(), lec_push(), send_to_lecd() and
lecd_attach()
- Use rcu_read_lock/rcu_dereference/rcu_read_unlock in send_to_lecd(),
lec_handle_bridge() and lec_atm_send() to safely access lecd
- Use rcu_assign_pointer() followed by synchronize_rcu() in
lec_atm_close() to ensure all readers have completed before
proceeding. This is safe since lec_atm_close() is called from
vcc_release() which holds lock_sock(), a sleeping lock.
- Remove the manual sk_receive_queue drain from lec_atm_close()
since vcc_destroy_socket() already drains it after lec_atm_close()
returns.
v2: Switch from spinlock + sock_hold/put approach to RCU to properly
fix the race. The v1 spinlock approach had two issues pointed out
by Eric Dumazet:
1. priv->lecd was still accessed directly after releasing the
lock instead of using a local copy.
2. The spinlock did not prevent packets being queued after
lec_atm_close() drains sk_receive_queue since timer and
workqueue paths bypass netif_stop_queue().
Note: Syzbot patch testing was attempted but the test VM terminated
unexpectedly with "Connection to localhost closed by remote host",
likely due to a QEMU AHCI emulation issue unrelated to this fix.
Compile testing with "make W=1 net/atm/lec.o" passes cleanly.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
|||||||||||||||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
No data.
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Fri, 01 May 2026 14:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: atm: lec: fix use-after-free in sock_def_readable() A race condition exists between lec_atm_close() setting priv->lecd to NULL and concurrent access to priv->lecd in send_to_lecd(), lec_handle_bridge(), and lec_atm_send(). When the socket is freed via RCU while another thread is still using it, a use-after-free occurs in sock_def_readable() when accessing the socket's wait queue. The root cause is that lec_atm_close() clears priv->lecd without any synchronization, while callers dereference priv->lecd without any protection against concurrent teardown. Fix this by converting priv->lecd to an RCU-protected pointer: - Mark priv->lecd as __rcu in lec.h - Use rcu_assign_pointer() in lec_atm_close() and lecd_attach() for safe pointer assignment - Use rcu_access_pointer() for NULL checks that do not dereference the pointer in lec_start_xmit(), lec_push(), send_to_lecd() and lecd_attach() - Use rcu_read_lock/rcu_dereference/rcu_read_unlock in send_to_lecd(), lec_handle_bridge() and lec_atm_send() to safely access lecd - Use rcu_assign_pointer() followed by synchronize_rcu() in lec_atm_close() to ensure all readers have completed before proceeding. This is safe since lec_atm_close() is called from vcc_release() which holds lock_sock(), a sleeping lock. - Remove the manual sk_receive_queue drain from lec_atm_close() since vcc_destroy_socket() already drains it after lec_atm_close() returns. v2: Switch from spinlock + sock_hold/put approach to RCU to properly fix the race. The v1 spinlock approach had two issues pointed out by Eric Dumazet: 1. priv->lecd was still accessed directly after releasing the lock instead of using a local copy. 2. The spinlock did not prevent packets being queued after lec_atm_close() drains sk_receive_queue since timer and workqueue paths bypass netif_stop_queue(). Note: Syzbot patch testing was attempted but the test VM terminated unexpectedly with "Connection to localhost closed by remote host", likely due to a QEMU AHCI emulation issue unrelated to this fix. Compile testing with "make W=1 net/atm/lec.o" passes cleanly. | |
| Title | atm: lec: fix use-after-free in sock_def_readable() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
Projects
Sign in to view the affected projects.
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-05-01T14:15:44.542Z
Reserved: 2026-05-01T14:12:55.979Z
Link: CVE-2026-43050
Vulnrichment
No data.
NVD
Status : Awaiting Analysis
Published: 2026-05-01T15:16:51.403
Modified: 2026-05-01T15:24:14.893
Link: CVE-2026-43050
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.