Calling kiocb_set_cancel_fn() without knowing whether the caller submitted a struct kiocb or a struct aio_kiocb is unsafe. Fix this by introducing the cancel_kiocb() method in struct file_operations. The following call trace illustrates that without this patch an out-of-bounds write happens if I/O is submitted by io_uring (from a phone with an ARM CPU and kernel 6.1): WARNING: CPU: 3 PID: 368 at fs/aio.c:598 kiocb_set_cancel_fn+0x9c/0xa8 Call trace: kiocb_set_cancel_fn+0x9c/0xa8 ffs_epfile_read_iter+0x144/0x1d0 io_read+0x19c/0x498 io_issue_sqe+0x118/0x27c io_submit_sqes+0x25c/0x5fc __arm64_sys_io_uring_enter+0x104/0xab0 invoke_syscall+0x58/0x11c el0_svc_common+0xb4/0xf4 do_el0_svc+0x2c/0xb0 el0_svc+0x2c/0xa4 el0t_64_sync_handler+0x68/0xb4 el0t_64_sync+0x1a4/0x1a8 The following patch has been used as the basis of this patch: Christoph Hellwig, "[PATCH 08/32] aio: replace kiocb_set_cancel_fn with a cancel_kiocb file operation", May 2018 (https://lore.kernel.org/all/20180515194833.6906-9-hch@xxxxxx/). Cc: Christoph Hellwig <hch@xxxxxx> Cc: Avi Kivity <avi@xxxxxxxxxxxx> Cc: Sandeep Dhavale <dhavale@xxxxxxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx> --- drivers/usb/gadget/function/f_fs.c | 10 +--- drivers/usb/gadget/legacy/inode.c | 5 +- fs/aio.c | 93 +++++++++++++++++------------- include/linux/aio.h | 7 --- include/linux/fs.h | 1 + include/linux/mm.h | 5 ++ include/linux/mm_inline.h | 5 ++ 7 files changed, 68 insertions(+), 58 deletions(-) diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 6bff6cb93789..adc00689fe3b 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -31,7 +31,6 @@ #include <linux/usb/composite.h> #include <linux/usb/functionfs.h> -#include <linux/aio.h> #include <linux/kthread.h> #include <linux/poll.h> #include <linux/eventfd.h> @@ -1157,7 +1156,7 @@ ffs_epfile_open(struct inode *inode, struct file *file) return stream_open(inode, file); } -static int ffs_aio_cancel(struct kiocb *kiocb) +static int ffs_epfile_cancel_kiocb(struct kiocb *kiocb) { struct ffs_io_data *io_data = kiocb->private; struct ffs_epfile *epfile = kiocb->ki_filp->private_data; @@ -1198,9 +1197,6 @@ static ssize_t ffs_epfile_write_iter(struct kiocb *kiocb, struct iov_iter *from) kiocb->private = p; - if (p->aio) - kiocb_set_cancel_fn(kiocb, ffs_aio_cancel); - res = ffs_epfile_io(kiocb->ki_filp, p); if (res == -EIOCBQUEUED) return res; @@ -1242,9 +1238,6 @@ static ssize_t ffs_epfile_read_iter(struct kiocb *kiocb, struct iov_iter *to) kiocb->private = p; - if (p->aio) - kiocb_set_cancel_fn(kiocb, ffs_aio_cancel); - res = ffs_epfile_io(kiocb->ki_filp, p); if (res == -EIOCBQUEUED) return res; @@ -1356,6 +1349,7 @@ static const struct file_operations ffs_epfile_operations = { .release = ffs_epfile_release, .unlocked_ioctl = ffs_epfile_ioctl, .compat_ioctl = compat_ptr_ioctl, + .cancel_kiocb = ffs_epfile_cancel_kiocb, }; diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c index 03179b1880fd..a4c03cfb3baa 100644 --- a/drivers/usb/gadget/legacy/inode.c +++ b/drivers/usb/gadget/legacy/inode.c @@ -22,7 +22,6 @@ #include <linux/slab.h> #include <linux/poll.h> #include <linux/kthread.h> -#include <linux/aio.h> #include <linux/uio.h> #include <linux/refcount.h> #include <linux/delay.h> @@ -446,7 +445,7 @@ struct kiocb_priv { unsigned actual; }; -static int ep_aio_cancel(struct kiocb *iocb) +static int ep_cancel_kiocb(struct kiocb *iocb) { struct kiocb_priv *priv = iocb->private; struct ep_data *epdata; @@ -537,7 +536,6 @@ static ssize_t ep_aio(struct kiocb *iocb, iocb->private = priv; priv->iocb = iocb; - kiocb_set_cancel_fn(iocb, ep_aio_cancel); get_ep(epdata); priv->epdata = epdata; priv->actual = 0; @@ -709,6 +707,7 @@ static const struct file_operations ep_io_operations = { .unlocked_ioctl = ep_ioctl, .read_iter = ep_read_iter, .write_iter = ep_write_iter, + .cancel_kiocb = ep_cancel_kiocb, }; /* ENDPOINT INITIALIZATION diff --git a/fs/aio.c b/fs/aio.c index bb2ff48991f3..0b13d6be773d 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -203,7 +203,6 @@ struct aio_kiocb { }; struct kioctx *ki_ctx; - kiocb_cancel_fn *ki_cancel; struct io_event ki_res; @@ -587,22 +586,6 @@ static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events) #define AIO_EVENTS_FIRST_PAGE ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event)) #define AIO_EVENTS_OFFSET (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE) -void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel) -{ - struct aio_kiocb *req = container_of(iocb, struct aio_kiocb, rw); - struct kioctx *ctx = req->ki_ctx; - unsigned long flags; - - if (WARN_ON_ONCE(!list_empty(&req->ki_list))) - return; - - spin_lock_irqsave(&ctx->ctx_lock, flags); - list_add_tail(&req->ki_list, &ctx->active_reqs); - req->ki_cancel = cancel; - spin_unlock_irqrestore(&ctx->ctx_lock, flags); -} -EXPORT_SYMBOL(kiocb_set_cancel_fn); - /* * free_ioctx() should be RCU delayed to synchronize against the RCU * protected lookup_ioctx() and also needs process context to call @@ -634,6 +617,8 @@ static void free_ioctx_reqs(struct percpu_ref *ref) queue_rcu_work(system_wq, &ctx->free_rwork); } +static void aio_cancel_and_del(struct aio_kiocb *req); + /* * When this function runs, the kioctx has been removed from the "hash table" * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted - @@ -649,8 +634,7 @@ static void free_ioctx_users(struct percpu_ref *ref) while (!list_empty(&ctx->active_reqs)) { req = list_first_entry(&ctx->active_reqs, struct aio_kiocb, ki_list); - req->ki_cancel(&req->rw); - list_del_init(&req->ki_list); + aio_cancel_and_del(req); } spin_unlock_irq(&ctx->ctx_lock); @@ -1556,6 +1540,20 @@ static inline void aio_rw_done(struct kiocb *req, ssize_t ret) { switch (ret) { case -EIOCBQUEUED: + /* + * If the .cancel_kiocb() callback has been set, add the request + * to the list of active requests. + */ + if (req->ki_filp->f_op->cancel_kiocb) { + struct aio_kiocb *iocb = + container_of(req, struct aio_kiocb, rw); + struct kioctx *ctx = iocb->ki_ctx; + unsigned long flags; + + spin_lock_irqsave(&ctx->ctx_lock, flags); + list_add_tail(&iocb->ki_list, &ctx->active_reqs); + spin_unlock_irqrestore(&ctx->ctx_lock, flags); + } break; case -ERESTARTSYS: case -ERESTARTNOINTR: @@ -1715,6 +1713,41 @@ static void poll_iocb_unlock_wq(struct poll_iocb *req) rcu_read_unlock(); } +/* assumes we are called with irqs disabled */ +static int aio_poll_cancel(struct aio_kiocb *aiocb) +{ + struct poll_iocb *req = &aiocb->poll; + struct kioctx *ctx = aiocb->ki_ctx; + + lockdep_assert_held(&ctx->ctx_lock); + + if (!poll_iocb_lock_wq(req)) { + /* Not a polled request or already cancelled. */ + return 0; + } + + WRITE_ONCE(req->cancelled, true); + if (!req->work_scheduled) { + schedule_work(&aiocb->poll.work); + req->work_scheduled = true; + } + poll_iocb_unlock_wq(req); + + return 0; +} + +static void aio_cancel_and_del(struct aio_kiocb *req) +{ + struct kioctx *ctx = req->ki_ctx; + + lockdep_assert_held(&ctx->ctx_lock); + + if (req->rw.ki_filp->f_op->cancel_kiocb) + req->rw.ki_filp->f_op->cancel_kiocb(&req->rw); + aio_poll_cancel(req); + list_del_init(&req->ki_list); +} + static void aio_poll_complete_work(struct work_struct *work) { struct poll_iocb *req = container_of(work, struct poll_iocb, work); @@ -1760,24 +1793,6 @@ static void aio_poll_complete_work(struct work_struct *work) iocb_put(iocb); } -/* assumes we are called with irqs disabled */ -static int aio_poll_cancel(struct kiocb *iocb) -{ - struct aio_kiocb *aiocb = container_of(iocb, struct aio_kiocb, rw); - struct poll_iocb *req = &aiocb->poll; - - if (poll_iocb_lock_wq(req)) { - WRITE_ONCE(req->cancelled, true); - if (!req->work_scheduled) { - schedule_work(&aiocb->poll.work); - req->work_scheduled = true; - } - poll_iocb_unlock_wq(req); - } /* else, the request was force-cancelled by POLLFREE already */ - - return 0; -} - static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, void *key) { @@ -1945,7 +1960,6 @@ static int aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb) * active_reqs so that it can be cancelled if needed. */ list_add_tail(&aiocb->ki_list, &ctx->active_reqs); - aiocb->ki_cancel = aio_poll_cancel; } if (on_queue) poll_iocb_unlock_wq(req); @@ -2189,8 +2203,7 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb, /* TODO: use a hash or array, this sucks. */ list_for_each_entry(kiocb, &ctx->active_reqs, ki_list) { if (kiocb->ki_res.obj == obj) { - ret = kiocb->ki_cancel(&kiocb->rw); - list_del_init(&kiocb->ki_list); + aio_cancel_and_del(kiocb); break; } } diff --git a/include/linux/aio.h b/include/linux/aio.h index 86892a4fe7c8..2aa6d0be3171 100644 --- a/include/linux/aio.h +++ b/include/linux/aio.h @@ -4,20 +4,13 @@ #include <linux/aio_abi.h> -struct kioctx; -struct kiocb; struct mm_struct; -typedef int (kiocb_cancel_fn)(struct kiocb *); - /* prototypes */ #ifdef CONFIG_AIO extern void exit_aio(struct mm_struct *mm); -void kiocb_set_cancel_fn(struct kiocb *req, kiocb_cancel_fn *cancel); #else static inline void exit_aio(struct mm_struct *mm) { } -static inline void kiocb_set_cancel_fn(struct kiocb *req, - kiocb_cancel_fn *cancel) { } #endif /* CONFIG_AIO */ #endif /* __LINUX__AIO_H */ diff --git a/include/linux/fs.h b/include/linux/fs.h index ed5966a70495..36cd982c167d 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2021,6 +2021,7 @@ struct file_operations { int (*uring_cmd)(struct io_uring_cmd *ioucmd, unsigned int issue_flags); int (*uring_cmd_iopoll)(struct io_uring_cmd *, struct io_comp_batch *, unsigned int poll_flags); + int (*cancel_kiocb)(struct kiocb *); } __randomize_layout; /* Wrap a directory iterator that needs exclusive inode access */ diff --git a/include/linux/mm.h b/include/linux/mm.h index f5a97dec5169..7c05464c0ad0 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1092,6 +1092,11 @@ static inline unsigned int folio_order(struct folio *folio) return folio->_flags_1 & 0xff; } +/* + * Include <linux/fs.h> to work around a circular dependency between + * <linux/fs.h> and <linux/huge_mm.h>. + */ +#include <linux/fs.h> #include <linux/huge_mm.h> /* diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index f4fe593c1400..4eb96f08ec4f 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -3,6 +3,11 @@ #define LINUX_MM_INLINE_H #include <linux/atomic.h> +/* + * Include <linux/fs.h> to work around a circular dependency between + * <linux/fs.h> and <linux/huge_mm.h>. + */ +#include <linux/fs.h> #include <linux/huge_mm.h> #include <linux/mm_types.h> #include <linux/swap.h>
