user/sven/linux.git/include, branch v6.6.93

NFS: Avoid flushing data while holding directory locks in nfs_rename()

2025-06-04T12:42:25Z

[ Upstream commit dcd21b609d4abc7303f8683bce4f35d78d7d6830 ] The Linux client assumes that all filehandles are non-volatile for renames within the same directory (otherwise sillyrename cannot work). However, the existence of the Linux 'subtree_check' export option has meant that nfs_rename() has always assumed it needs to flush writes before attempting to rename. Since NFSv4 does allow the client to query whether or not the server exhibits this behaviour, and since knfsd does actually set the appropriate flag when 'subtree_check' is enabled on an export, it should be OK to optimise away the write flushing behaviour in the cases where it is clearly not needed. Signed-off-by: Trond Myklebust Reviewed-by: Jeff Layton Signed-off-by: Sasha Levin

coredump: hand a pidfd to the usermode coredump helper

2025-06-04T12:42:24Z

commit b5325b2a270fcaf7b2a9a0f23d422ca8a5a8bdea upstream. Give userspace a way to instruct the kernel to install a pidfd into the usermode helper process. This makes coredump handling a lot more reliable for userspace. In parallel with this commit we already have systemd adding support for this in [1]. We create a pidfs file for the coredumping process when we process the corename pattern. When the usermode helper process is forked we then install the pidfs file as file descriptor three into the usermode helpers file descriptor table so it's available to the exec'd program. Since usermode helpers are either children of the system_unbound_wq workqueue or kthreadd we know that the file descriptor table is empty and can thus always use three as the file descriptor number. Note, that we'll install a pidfd for the thread-group leader even if a subthread is calling do_coredump(). We know that task linkage hasn't been removed due to delay_group_leader() and even if this @current isn't the actual thread-group leader we know that the thread-group leader cannot be reaped until @current has exited. [brauner: This is a backport for the v6.6 series. Upsteam has significantly changed and backporting all that infra is a non-starter. So simply use the pidfd_prepare() helper and waste the file descriptor we allocated. Then we minimally massage the umh coredump setup code.] Link: https://github.com/systemd/systemd/pull/37125 [1] Link: https://lore.kernel.org/20250414-work-coredump-v2-3-685bf231f828@kernel.org Tested-by: Luca Boccassi Reviewed-by: Oleg Nesterov Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman

af_unix: Add dead flag to struct scm_fp_list.

2025-06-04T12:42:24Z

commit 7172dc93d621d5dc302d007e95ddd1311ec64283 upstream. Commit 1af2dface5d2 ("af_unix: Don't access successor in unix_del_edges() during GC.") fixed use-after-free by avoid accessing edge->successor while GC is in progress. However, there could be a small race window where another process could call unix_del_edges() while gc_in_progress is true and __skb_queue_purge() is on the way. So, we need another marker for struct scm_fp_list which indicates if the skb is garbage-collected. This patch adds dead flag in struct scm_fp_list and set it true before calling __skb_queue_purge(). Fixes: 1af2dface5d2 ("af_unix: Don't access successor in unix_del_edges() during GC.") Signed-off-by: Kuniyuki Iwashima Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20240508171150.50601-1-kuniyu@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

af_unix: Try not to hold unix_gc_lock during accept().

2025-06-04T12:42:23Z

commit fd86344823b521149bb31d91eba900ba3525efa6 upstream. Commit dcf70df2048d ("af_unix: Fix up unix_edge.successor for embryo socket.") added spin_lock(&unix_gc_lock) in accept() path, and it caused regression in a stress test as reported by kernel test robot. If the embryo socket is not part of the inflight graph, we need not hold the lock. To decide that in O(1) time and avoid the regression in the normal use case, 1. add a new stat unix_sk(sk)->scm_stat.nr_unix_fds 2. count the number of inflight AF_UNIX sockets in the receive queue under unix_state_lock() 3. move unix_update_edges() call under unix_state_lock() 4. avoid locking if nr_unix_fds is 0 in unix_update_edges() Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202404101427.92a08551-oliver.sang@intel.com Signed-off-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20240413021928.20946-1-kuniyu@amazon.com Signed-off-by: Paolo Abeni Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

af_unix: Remove lock dance in unix_peek_fds().

2025-06-04T12:42:23Z

commit 118f457da9ed58a79e24b73c2ef0aa1987241f0e upstream. In the previous GC implementation, the shape of the inflight socket graph was not expected to change while GC was in progress. MSG_PEEK was tricky because it could install inflight fd silently and transform the graph. Let's say we peeked a fd, which was a listening socket, and accept()ed some embryo sockets from it. The garbage collection algorithm would have been confused because the set of sockets visited in scan_inflight() would change within the same GC invocation. That's why we placed spin_lock(&unix_gc_lock) and spin_unlock() in unix_peek_fds() with a fat comment. In the new GC implementation, we no longer garbage-collect the socket if it exists in another queue, that is, if it has a bridge to another SCC. Also, accept() will require the lock if it has edges. Thus, we need not do the complicated lock dance. Signed-off-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20240401173125.92184-3-kuniyu@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

af_unix: Replace garbage collection algorithm.

2025-06-04T12:42:23Z

commit 4090fa373f0e763c43610853d2774b5979915959 upstream. If we find a dead SCC during iteration, we call unix_collect_skb() to splice all skb in the SCC to the global sk_buff_head, hitlist. After iterating all SCC, we unlock unix_gc_lock and purge the queue. Signed-off-by: Kuniyuki Iwashima Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20240325202425.60930-15-kuniyu@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

af_unix: Assign a unique index to SCC.

2025-06-04T12:42:23Z

commit bfdb01283ee8f2f3089656c3ff8f62bb072dabb2 upstream. The definition of the lowlink in Tarjan's algorithm is the smallest index of a vertex that is reachable with at most one back-edge in SCC. This is not useful for a cross-edge. If we start traversing from A in the following graph, the final lowlink of D is 3. The cross-edge here is one between D and C. A -> B -> D D = (4, 3) (index, lowlink) ^ | | C = (3, 1) | V | B = (2, 1) `--- C <--' A = (1, 1) This is because the lowlink of D is updated with the index of C. In the following patch, we detect a dead SCC by checking two conditions for each vertex. 1) vertex has no edge directed to another SCC (no bridge) 2) vertex's out_degree is the same as the refcount of its file If 1) is false, there is a receiver of all fds of the SCC and its ancestor SCC. To evaluate 1), we need to assign a unique index to each SCC and assign it to all vertices in the SCC. This patch changes the lowlink update logic for cross-edge so that in the example above, the lowlink of D is updated with the lowlink of C. A -> B -> D D = (4, 1) (index, lowlink) ^ | | C = (3, 1) | V | B = (2, 1) `--- C <--' A = (1, 1) Then, all vertices in the same SCC have the same lowlink, and we can quickly find the bridge connecting to different SCC if exists. However, it is no longer called lowlink, so we rename it to scc_index. (It's sometimes called lowpoint.) Also, we add a global variable to hold the last index used in DFS so that we do not reset the initial index in each DFS. This patch can be squashed to the SCC detection patch but is split deliberately for anyone wondering why lowlink is not used as used in the original Tarjan's algorithm and many reference implementations. Signed-off-by: Kuniyuki Iwashima Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20240325202425.60930-13-kuniyu@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

af_unix: Save O(n) setup of Tarjan's algo.

2025-06-04T12:42:23Z

commit ba31b4a4e1018f5844c6eb31734976e2184f2f9a upstream. Before starting Tarjan's algorithm, we need to mark all vertices as unvisited. We can save this O(n) setup by reserving two special indices (0, 1) and using two variables. The first time we link a vertex to unix_unvisited_vertices, we set unix_vertex_unvisited_index to index. During DFS, we can see that the index of unvisited vertices is the same as unix_vertex_unvisited_index. When we finalise SCC later, we set unix_vertex_grouped_index to each vertex's index. Then, we can know (i) that the vertex is on the stack if the index of a visited vertex is >= 2 and (ii) that it is not on the stack and belongs to a different SCC if the index is unix_vertex_grouped_index. After the whole algorithm, all indices of vertices are set as unix_vertex_grouped_index. Next time we start DFS, we know that all unvisited vertices have unix_vertex_grouped_index, and we can use unix_vertex_unvisited_index as the not-on-stack marker. To use the same variable in __unix_walk_scc(), we can swap unix_vertex_(grouped|unvisited)_index at the end of Tarjan's algorithm. Signed-off-by: Kuniyuki Iwashima Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20240325202425.60930-10-kuniyu@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

af_unix: Fix up unix_edge.successor for embryo socket.

2025-06-04T12:42:23Z

commit dcf70df2048d27c5d186f013f101a4aefd63aa41 upstream. To garbage collect inflight AF_UNIX sockets, we must define the cyclic reference appropriately. This is a bit tricky if the loop consists of embryo sockets. Suppose that the fd of AF_UNIX socket A is passed to D and the fd B to C and that C and D are embryo sockets of A and B, respectively. It may appear that there are two separate graphs, A (-> D) and B (-> C), but this is not correct. A --. .-- B X C <-' `-> D Now, D holds A's refcount, and C has B's refcount, so unix_release() will never be called for A and B when we close() them. However, no one can call close() for D and C to free skbs holding refcounts of A and B because C/D is in A/B's receive queue, which should have been purged by unix_release() for A and B. So, here's another type of cyclic reference. When a fd of an AF_UNIX socket is passed to an embryo socket, the reference is indirectly held by its parent listening socket. .-> A .-> B | `- sk_receive_queue | `- sk_receive_queue | `- skb | `- skb | `- sk == C | `- sk == D | `- sk_receive_queue | `- sk_receive_queue | `- skb +---------' `- skb +-. | | `---------------------------------------------------------' Technically, the graph must be denoted as A <-> B instead of A (-> D) and B (-> C) to find such a cyclic reference without touching each socket's receive queue. .-> A --. .-- B <-. | X | == A <-> B `-- C <-' `-> D --' We apply this fixup during GC by fetching the real successor by unix_edge_successor(). When we call accept(), we clear unix_sock.listener under unix_gc_lock not to confuse GC. Signed-off-by: Kuniyuki Iwashima Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20240325202425.60930-9-kuniyu@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

af_unix: Save listener for embryo socket.

2025-06-04T12:42:23Z

commit aed6ecef55d70de3762ce41c561b7f547dbaf107 upstream. This is a prep patch for the following change, where we need to fetch the listening socket from the successor embryo socket during GC. We add a new field to struct unix_sock to save a pointer to a listening socket. We set it when connect() creates a new socket, and clear it when accept() is called. Signed-off-by: Kuniyuki Iwashima Acked-by: Paolo Abeni Link: https://lore.kernel.org/r/20240325202425.60930-8-kuniyu@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman