7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ian Bridges [ Upstream commit 248b5819591c577727930e4e255a455235fab50a ] ksmbd_reopen_durable_fd() republishes a detached durable handle in the reconnecting session's file table and takes no reference for that entry. If smb2_open() then fails, cleanup relies on the final ksmbd_fd_put() to remove the volatile id. Two reconnects of the same handle can both take a lookup reference before either attaches it. If the one that reopens first then fails and drops its references first, the other request makes the final put through ksmbd_put_durable_fd(). That frees the handle without removing the first session's table entry, so tearing that session down writes to freed memory. BUG: KASAN: slab-use-after-free in __close_file_table_ids+0x14d/0x740 [ksmbd] Call Trace: __close_file_table_ids+0x14d/0x740 [ksmbd] ksmbd_destroy_file_table+0x76/0x100 [ksmbd] ksmbd_session_destroy+0xf8/0x480 [ksmbd] ksmbd_dispose_sessions+0x13e/0x200 [ksmbd] ksmbd_conn_sessions_cleanup+0x4c3/0x6d0 [ksmbd] Freed by task 1030: __ksmbd_close_fd+0x97d/0x1000 [ksmbd] smb2_open+0x14eb/0xd9f0 [ksmbd] Commit 3515503322f4 ("ksmbd: fix durable reconnect error path file lifetime") handles a final put made by the reconnecting request, but not one made by another holder. Remove the volatile id under the file-table lock on this error path, before the references are dropped, as ksmbd_close_fd() does on the request_open path just above. Removal then no longer depends on which holder makes the final put. The stale comment in the reconnect cleanup is updated to match. A successful reconnect is unchanged. Fixes: c8efcc786146 ("ksmbd: add support for durable handles v1/v2") Cc: stable@vger.kernel.org Signed-off-by: Ian Bridges Signed-off-by: Namjae Jeon Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/smb/server/smb2pdu.c | 9 +++++---- fs/smb/server/vfs_cache.c | 28 ++++++++++++++++++++++++++++ fs/smb/server/vfs_cache.h | 2 ++ 3 files changed, 35 insertions(+), 4 deletions(-) --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -5525,6 +5525,8 @@ err_out2: ksmbd_close_fd(work, fp->volatile_id); smb2_complete_request_open(work); } else { + if (dh_info.reconnected && fp == dh_info.fp) + ksmbd_unpublish_reopened_fd(work, fp); ksmbd_fd_put(work, fp); } } @@ -5538,10 +5540,9 @@ err_out2: if (dh_info.reconnected) { /* * If reconnect succeeded, fp was republished in the - * session file table. On a later error, ksmbd_fd_put() - * above drops the session reference; drop the durable - * lookup reference through the same session-aware path so - * final close removes the volatile id before freeing fp. + * session file table, and the error path above has + * already removed its volatile id. Drop the durable + * lookup reference through the same session-aware path. */ if (rc && fp == dh_info.fp) ksmbd_fd_put(work, dh_info.fp); --- a/fs/smb/server/vfs_cache.c +++ b/fs/smb/server/vfs_cache.c @@ -851,6 +851,34 @@ void ksmbd_wake_session_blocked_works(st read_unlock(&ft->lock); } +/** + * ksmbd_unpublish_reopened_fd() - remove a reopened durable handle from the + * session file table after its CREATE failed + * @work: smb work of the failed CREATE + * @fp: durable handle republished by ksmbd_reopen_durable_fd() + * + * The reopen publishes @fp in this session's table without taking a reference + * for the entry, so the CREATE error path's puts need not be the last ones. + * Another holder of a global-table reference, such as a concurrent reconnect + * of the same handle, can drop the last one through ksmbd_put_durable_fd(), + * which frees @fp without touching this table. Remove the id here, while + * the caller still holds its references. + * + * Every path that removes the id before the final put also clears + * @fp->volatile_id under ft->lock, so a valid id is still @fp's entry. + */ +void ksmbd_unpublish_reopened_fd(struct ksmbd_work *work, struct ksmbd_file *fp) +{ + struct ksmbd_file_table *ft = &work->sess->file_table; + + write_lock(&ft->lock); + if (has_file_id(fp->volatile_id)) { + idr_remove(ft->idr, fp->volatile_id); + fp->volatile_id = KSMBD_NO_FID; + } + write_unlock(&ft->lock); +} + int ksmbd_close_fd(struct ksmbd_work *work, u64 id) { struct ksmbd_file *fp; --- a/fs/smb/server/vfs_cache.h +++ b/fs/smb/server/vfs_cache.h @@ -198,6 +198,8 @@ static inline bool ksmbd_stream_fd(struc int ksmbd_init_file_table(struct ksmbd_file_table *ft); void ksmbd_destroy_file_table(struct ksmbd_session *sess); int ksmbd_close_fd(struct ksmbd_work *work, u64 id); +void ksmbd_unpublish_reopened_fd(struct ksmbd_work *work, + struct ksmbd_file *fp); struct ksmbd_file *ksmbd_lookup_fd_fast(struct ksmbd_work *work, u64 id); struct ksmbd_file *ksmbd_lookup_foreign_fd(struct ksmbd_work *work, u64 id); struct ksmbd_file *ksmbd_lookup_fd_slow(struct ksmbd_work *work, u64 id,