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| author | Namjae Jeon <linkinjeon@kernel.org> | 2026-03-07 11:32:31 +0900 |
|---|---|---|
| committer | Steve French <stfrench@microsoft.com> | 2026-03-08 21:28:39 -0500 |
| commit | 1dfd062caa165ec9d7ee0823087930f3ab8a6294 (patch) | |
| tree | f2aede1eaf756939273d2245c7397b2df476bc7a | |
| parent | 40955015fae4908157ac6c959ea696d05e6e9b31 (diff) | |
| download | linux-1dfd062caa165ec9d7ee0823087930f3ab8a6294.tar.gz linux-1dfd062caa165ec9d7ee0823087930f3ab8a6294.zip | |
ksmbd: fix use-after-free by using call_rcu() for oplock_info
ksmbd currently frees oplock_info immediately using kfree(), even
though it is accessed under RCU read-side critical sections in places
like opinfo_get() and proc_show_files().
Since there is no RCU grace period delay between nullifying the pointer
and freeing the memory, a reader can still access oplock_info
structure after it has been freed. This can leads to a use-after-free
especially in opinfo_get() where atomic_inc_not_zero() is called on
already freed memory.
Fix this by switching to deferred freeing using call_rcu().
Fixes: 18b4fac5ef17 ("ksmbd: fix use-after-free in smb_break_all_levII_oplock()")
Cc: stable@vger.kernel.org
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
| -rw-r--r-- | fs/smb/server/oplock.c | 29 | ||||
| -rw-r--r-- | fs/smb/server/oplock.h | 5 |
2 files changed, 24 insertions, 10 deletions
diff --git a/fs/smb/server/oplock.c b/fs/smb/server/oplock.c index 09d9878db9cb..8c9aa17384f3 100644 --- a/fs/smb/server/oplock.c +++ b/fs/smb/server/oplock.c @@ -120,7 +120,7 @@ static void free_lease(struct oplock_info *opinfo) kfree(lease); } -static void free_opinfo(struct oplock_info *opinfo) +static void __free_opinfo(struct oplock_info *opinfo) { if (opinfo->is_lease) free_lease(opinfo); @@ -129,6 +129,18 @@ static void free_opinfo(struct oplock_info *opinfo) kfree(opinfo); } +static void free_opinfo_rcu(struct rcu_head *rcu) +{ + struct oplock_info *opinfo = container_of(rcu, struct oplock_info, rcu); + + __free_opinfo(opinfo); +} + +static void free_opinfo(struct oplock_info *opinfo) +{ + call_rcu(&opinfo->rcu, free_opinfo_rcu); +} + struct oplock_info *opinfo_get(struct ksmbd_file *fp) { struct oplock_info *opinfo; @@ -176,9 +188,9 @@ void opinfo_put(struct oplock_info *opinfo) free_opinfo(opinfo); } -static void opinfo_add(struct oplock_info *opinfo) +static void opinfo_add(struct oplock_info *opinfo, struct ksmbd_file *fp) { - struct ksmbd_inode *ci = opinfo->o_fp->f_ci; + struct ksmbd_inode *ci = fp->f_ci; down_write(&ci->m_lock); list_add(&opinfo->op_entry, &ci->m_op_list); @@ -1277,20 +1289,21 @@ set_lev: set_oplock_level(opinfo, req_op_level, lctx); out: - rcu_assign_pointer(fp->f_opinfo, opinfo); - opinfo->o_fp = fp; - opinfo_count_inc(fp); - opinfo_add(opinfo); + opinfo_add(opinfo, fp); + if (opinfo->is_lease) { err = add_lease_global_list(opinfo); if (err) goto err_out; } + rcu_assign_pointer(fp->f_opinfo, opinfo); + opinfo->o_fp = fp; + return 0; err_out: - free_opinfo(opinfo); + __free_opinfo(opinfo); return err; } diff --git a/fs/smb/server/oplock.h b/fs/smb/server/oplock.h index 9a56eaadd0dd..921e3199e4df 100644 --- a/fs/smb/server/oplock.h +++ b/fs/smb/server/oplock.h @@ -69,8 +69,9 @@ struct oplock_info { struct lease *o_lease; struct list_head op_entry; struct list_head lease_entry; - wait_queue_head_t oplock_q; /* Other server threads */ - wait_queue_head_t oplock_brk; /* oplock breaking wait */ + wait_queue_head_t oplock_q; /* Other server threads */ + wait_queue_head_t oplock_brk; /* oplock breaking wait */ + struct rcu_head rcu; }; struct lease_break_info { |