kernel/linux.git/net/9p, branch v6.1.178

net/9p: fix infinite loop in p9_client_rpc on fatal signal

2026-07-24T13:55:03+00:00

commit 6b4f48728faa8bb514368f7eacda05565dea8696 upstream. When p9_client_rpc() is called with type P9_TFLUSH and the transport has no peer (e.g. fd transport backed by pipes with no 9p server), a fatal signal causes an infinite loop: again: err = io_wait_event_killable(req->wq, ...) /* SIGKILL wakes the task, returns -ERESTARTSYS */ if (err == -ERESTARTSYS && c->status == Connected && type == P9_TFLUSH) { sigpending = 1; clear_thread_flag(TIF_SIGPENDING); goto again; } clear_thread_flag() clears TIF_SIGPENDING before jumping back to io_wait_event_killable(). signal_pending_state() checks TIF_SIGPENDING, finds it zero, and the task goes to sleep again. The task can only wake on the next signal delivery that calls signal_wake_up() and sets TIF_SIGPENDING again. When that happens the loop repeats, clears TIF_SIGPENDING, and sleeps again indefinitely. This is triggered in practice by coredump_wait(): when a thread in a multi-threaded process causes a coredump (e.g. via SIGSYS from Syscall User Dispatch), coredump_wait() sends SIGKILL to all other threads and waits for them to call mm_release(). If one of those threads is blocked in p9_client_rpc() over an fd transport with no peer, it enters the P9_TFLUSH loop and never calls mm_release(), so coredump_wait() stalls forever: INFO: task syz.0.18:676 blocked for more than 143 seconds. Not tainted 6.12.77+ #1 task:syz.0.18 state:D stack:27600 pid:676 tgid:673 ppid:630 flags:0x00000004 Call Trace: context_switch kernel/sched/core.c:5344 [inline] __schedule+0xcb4/0x5d50 kernel/sched/core.c:6724 __schedule_loop kernel/sched/core.c:6801 [inline] schedule+0xe5/0x350 kernel/sched/core.c:6816 schedule_timeout+0x253/0x290 kernel/time/timer.c:2593 do_wait_for_common kernel/sched/completion.c:95 [inline] __wait_for_common+0x409/0x600 kernel/sched/completion.c:116 wait_for_common kernel/sched/completion.c:127 [inline] wait_for_completion_state+0x1d/0x40 kernel/sched/completion.c:264 coredump_wait fs/coredump.c:448 [inline] do_coredump+0x854/0x4350 fs/coredump.c:629 get_signal+0x1425/0x2730 kernel/signal.c:2903 arch_do_signal_or_restart+0x81/0x880 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop kernel/entry/common.c:111 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0xf9/0x160 kernel/entry/common.c:218 do_syscall_64+0x102/0x220 arch/x86/entry/common.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fix: check fatal_signal_pending() before clearing TIF_SIGPENDING in the P9_TFLUSH retry loop. At that point TIF_SIGPENDING is still set, so fatal_signal_pending() works correctly. If a fatal signal is pending, jump to recalc_sigpending to restore TIF_SIGPENDING and return -ERESTARTSYS to the caller. The same defect is present in stable kernels back to 5.4. On those kernels the infinite loop is broken earlier by a second SIGKILL from the parent process (e.g. kill_and_wait() retrying after a timeout), resulting in a zombie process and a shutdown delay rather than a permanent D-state hang, but the underlying flaw is the same. Found by Linux Verification Center (linuxtesting.org) with Syzkaller. Fixes: 91b8534fa8f5 ("9p: make rpc code common and rework flush code") Closes: https://syzkaller.appspot.com/bug?extid=3ce7863f8fc836a427e7 Cc: stable@vger.kernel.org Signed-off-by: Vasiliy Kovalev Message-ID: <20260415155237.182891-1-kovalev@altlinux.org> Signed-off-by: Dominique Martinet Signed-off-by: Greg Kroah-Hartman

net/9p: fix race condition on rdma->state in trans_rdma.c

2026-07-24T13:54:44+00:00

[ Upstream commit 7d54894a1ee265a72d70f7cae1da6cc774cccc71 ] The rdma->state field is modified without holding req_lock in both recv_done() and p9_cm_event_handler(), while rdma_request() accesses the same field under the req_lock spinlock. This inconsistent locking creates a race condition: - recv_done() running in softirq completion context sets rdma->state = P9_RDMA_FLUSHING without acquiring req_lock - p9_cm_event_handler() modifies rdma->state at multiple points (ADDR_RESOLVED, ROUTE_RESOLVED, ESTABLISHED, CLOSED) without req_lock - rdma_request() uses spin_lock_irqsave(&rdma->req_lock, flags) to protect the read-modify-write of rdma->state The race can cause lost state transitions: recv_done() or the CM event handler could set state to FLUSHING/CLOSED while rdma_request() is concurrently checking or modifying state under the lock, leading to the FLUSHING transition being silently overwritten by CLOSING. This corrupts the connection state machine and can cause use-after-free on RDMA request objects during teardown. Fix by adding req_lock protection to all rdma->state modifications in recv_done() and p9_cm_event_handler(), matching the pattern already used in rdma_request(). Use spin_lock_irqsave/spin_unlock_irqrestore in the CM event handler since it can race with recv_done() which runs in softirq context. Tested with a kernel module that races two threads (simulating rdma_request and recv_done/CM handler) on rdma->state with proper locking: 5.5M+ FLUSHING writes over 27M iterations with 0 lost transitions. Fixes: 473c7dd1d7b5 ("9p/rdma: remove useless check in cm_event_handler") Reported-by: Yizhou Zhao Reported-by: Yuxiang Yang Reported-by: Ao Wang Reported-by: Xuewei Feng Reported-by: Qi Li Reported-by: Ke Xu Assisted-by: GLM:GLM-5.1 Signed-off-by: Yizhou Zhao Message-ID: <20260529073933.77315-1-zhaoyz24@mails.tsinghua.edu.cn> Signed-off-by: Dominique Martinet Signed-off-by: Sasha Levin

9p: avoid putting oldfid in p9_client_walk() error path

2026-07-04T11:41:32+00:00

commit 1a3860d46e3eb47dbd60339783cdad7904486b9f upstream. When p9_client_walk() is called with clone set to false, fid aliases oldfid. If the walk subsequently fails after the request has been sent, the error path jumps to clunk_fid, which currently calls p9_fid_put(fid) unconditionally. This drops a reference to oldfid even though ownership of oldfid remains with the caller. If this is the last reference, oldfid can be clunked and destroyed while the caller still expects it to be valid. A later use or put of oldfid can then trigger a use-after-free or refcount underflow. Fix this by only putting fid in the clunk_fid error path when it does not alias oldfid, matching the existing guard in the error path below. This can be triggered when a multi-component walk is split into multiple p9_client_walk() calls and a later non-cloning walk fails. A reproducer and refcount warning logs are available on request. Fixes: b48dbb998d70 ("9p fid refcount: add p9_fid_get/put wrappers") Cc: stable@vger.kernel.org Reported-by: Yuxiang Yang Reported-by: Ao Wang Reported-by: Xuewei Feng Reported-by: Qi Li Reported-by: Ke Xu Assisted-by: GLM 5.1 Signed-off-by: Yizhou Zhao Message-ID: <20260528053918.53550-1-zhaoyz24@mails.tsinghua.edu.cn> Signed-off-by: Dominique Martinet Signed-off-by: Greg Kroah-Hartman

xen: make remove callback of xen driver void returned

2026-02-06T15:44:18+00:00

[ Upstream commit 7cffcade57a429667447c4f41d8414bbcf1b3aaa ] Since commit fc7a6209d571 ("bus: Make remove callback return void") forces bus_type::remove be void-returned, it doesn't make much sense for any bus based driver implementing remove callbalk to return non-void to its caller. This change is for xen bus based drivers. Acked-by: Juergen Gross Signed-off-by: Dawei Li Link: https://lore.kernel.org/r/TYCP286MB23238119AB4DF190997075C9CAE39@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM Signed-off-by: Juergen Gross Stable-dep-of: 901a5f309dab ("scsi: xen: scsiback: Fix potential memory leak in scsiback_remove()") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

net/9p: fix double req put in p9_fd_cancelled

2025-10-15T09:56:25+00:00

commit 674b56aa57f9379854cb6798c3bbcef7e7b51ab7 upstream. Syzkaller reports a KASAN issue as below: general protection fault, probably for non-canonical address 0xfbd59c0000000021: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: maybe wild-memory-access in range [0xdead000000000108-0xdead00000000010f] CPU: 0 PID: 5083 Comm: syz-executor.2 Not tainted 6.1.134-syzkaller-00037-g855bd1d7d838 #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:__list_del include/linux/list.h:114 [inline] RIP: 0010:__list_del_entry include/linux/list.h:137 [inline] RIP: 0010:list_del include/linux/list.h:148 [inline] RIP: 0010:p9_fd_cancelled+0xe9/0x200 net/9p/trans_fd.c:734 Call Trace: p9_client_flush+0x351/0x440 net/9p/client.c:614 p9_client_rpc+0xb6b/0xc70 net/9p/client.c:734 p9_client_version net/9p/client.c:920 [inline] p9_client_create+0xb51/0x1240 net/9p/client.c:1027 v9fs_session_init+0x1f0/0x18f0 fs/9p/v9fs.c:408 v9fs_mount+0xba/0xcb0 fs/9p/vfs_super.c:126 legacy_get_tree+0x108/0x220 fs/fs_context.c:632 vfs_get_tree+0x8e/0x300 fs/super.c:1573 do_new_mount fs/namespace.c:3056 [inline] path_mount+0x6a6/0x1e90 fs/namespace.c:3386 do_mount fs/namespace.c:3399 [inline] __do_sys_mount fs/namespace.c:3607 [inline] __se_sys_mount fs/namespace.c:3584 [inline] __x64_sys_mount+0x283/0x300 fs/namespace.c:3584 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 This happens because of a race condition between: - The 9p client sending an invalid flush request and later cleaning it up; - The 9p client in p9_read_work() canceled all pending requests. Thread 1 Thread 2 ... p9_client_create() ... p9_fd_create() ... p9_conn_create() ... // start Thread 2 INIT_WORK(&m->rq, p9_read_work); p9_read_work() ... p9_client_rpc() ... ... p9_conn_cancel() ... spin_lock(&m->req_lock); ... p9_fd_cancelled() ... ... spin_unlock(&m->req_lock); // status rewrite p9_client_cb(m->client, req, REQ_STATUS_ERROR) // first remove list_del(&req->req_list); ... spin_lock(&m->req_lock) ... // second remove list_del(&req->req_list); spin_unlock(&m->req_lock) ... Commit 74d6a5d56629 ("9p/trans_fd: Fix concurrency del of req_list in p9_fd_cancelled/p9_read_work") fixes a concurrency issue in the 9p filesystem client where the req_list could be deleted simultaneously by both p9_read_work and p9_fd_cancelled functions, but for the case where req->status equals REQ_STATUS_RCVD. Update the check for req->status in p9_fd_cancelled to skip processing not just received requests, but anything that is not SENT, as whatever changed the state from SENT also removed the request from its list. Found by Linux Verification Center (linuxtesting.org) with Syzkaller. Fixes: afd8d6541155 ("9P: Add cancelled() to the transport functions.") Cc: stable@vger.kernel.org Signed-off-by: Nalivayko Sergey Message-ID: <20250715154815.3501030-1-Sergey.Nalivayko@kaspersky.com> [updated the check from status == RECV || status == ERROR to status != SENT] Signed-off-by: Dominique Martinet Signed-off-by: Greg Kroah-Hartman

9p/net: fix improper handling of bogus negative read/write replies

2025-05-02T05:47:04+00:00

[ Upstream commit d0259a856afca31d699b706ed5e2adf11086c73b ] In p9_client_write() and p9_client_read_once(), if the server incorrectly replies with success but a negative write/read count then we would consider written (negative) <= rsize (positive) because both variables were signed. Make variables unsigned to avoid this problem. The reproducer linked below now fails with the following error instead of a null pointer deref: 9pnet: bogus RWRITE count (4294967295 > 3) Reported-by: Robert Morris Closes: https://lore.kernel.org/16271.1734448631@26-5-164.dynamic.csail.mit.edu Message-ID: <20250319-9p_unsigned_rw-v3-1-71327f1503d0@codewreck.org> Reviewed-by: Christian Schoenebeck Signed-off-by: Dominique Martinet Signed-off-by: Sasha Levin

9p/xen: fix release of IRQ

2024-12-14T18:54:08+00:00

[ Upstream commit e43c608f40c065b30964f0a806348062991b802d ] Kernel logs indicate an IRQ was double-freed. Pass correct device ID during IRQ release. Fixes: 71ebd71921e45 ("xen/9pfs: connect to the backend") Signed-off-by: Alex Zenla Signed-off-by: Alexander Merritt Signed-off-by: Ariadne Conill Reviewed-by: Juergen Gross Message-ID: <20241121225100.5736-1-alexander@edera.dev> [Dominique: remove confusing variable reset to 0] Signed-off-by: Dominique Martinet Signed-off-by: Sasha Levin

9p/xen: fix init sequence

2024-12-14T18:54:08+00:00

[ Upstream commit 7ef3ae82a6ebbf4750967d1ce43bcdb7e44ff74b ] Large amount of mount hangs observed during hotplugging of 9pfs devices. The 9pfs Xen driver attempts to initialize itself more than once, causing the frontend and backend to disagree: the backend listens on a channel that the frontend does not send on, resulting in stalled processing. Only allow initialization of 9p frontend once. Fixes: c15fe55d14b3b ("9p/xen: fix connection sequence") Signed-off-by: Alex Zenla Signed-off-by: Alexander Merritt Signed-off-by: Ariadne Conill Reviewed-by: Juergen Gross Message-ID: <20241119211633.38321-1-alexander@edera.dev> Signed-off-by: Dominique Martinet Signed-off-by: Sasha Levin

9p: fix slab cache name creation for real

2024-11-17T14:07:22+00:00

commit a360f311f57a36e96d88fa8086b749159714dcd2 upstream. This was attempted by using the dev_name in the slab cache name, but as Omar Sandoval pointed out, that can be an arbitrary string, eg something like "/dev/root". Which in turn trips verify_dirent_name(), which fails if a filename contains a slash. So just make it use a sequence counter, and make it an atomic_t to avoid any possible races or locking issues. Reported-and-tested-by: Omar Sandoval Link: https://lore.kernel.org/all/ZxafcO8KWMlXaeWE@telecaster.dhcp.thefacebook.com/ Fixes: 79efebae4afc ("9p: Avoid creating multiple slab caches with the same name") Acked-by: Vlastimil Babka Cc: Dominique Martinet Cc: Thorsten Leemhuis Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

9p: Avoid creating multiple slab caches with the same name

2024-11-17T14:07:20+00:00

[ Upstream commit 79efebae4afc2221fa814c3cae001bede66ab259 ] In the spirit of [1], avoid creating multiple slab caches with the same name. Instead, add the dev_name into the mix. [1]: https://lore.kernel.org/all/20240807090746.2146479-1-pedro.falcato@gmail.com/ Signed-off-by: Pedro Falcato Reported-by: syzbot+3c5d43e97993e1fa612b@syzkaller.appspotmail.com Message-ID: <20240807094725.2193423-1-pedro.falcato@gmail.com> Signed-off-by: Dominique Martinet Signed-off-by: Sasha Levin