From: "Matthew Wilcox (Oracle)" willy@infradead.org
commit 61cf93700fe6359552848ed5e3becba6cd760efa upstream.
You can't call idr_remove() from within a idr_for_each() callback, but you can call xa_erase() from an xa_for_each() loop, so switch the entire personality_idr from the IDR to the XArray. This manifests as a use-after-free as idr_for_each() attempts to walk the rest of the node after removing the last entry from it.
Fixes: 071698e13ac6 ("io_uring: allow registering credentials") Cc: stable@vger.kernel.org # 5.6+ Reported-by: yangerkun yangerkun@huawei.com Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org [Pavel: rebased (creds load was moved into io_init_req())] Signed-off-by: Pavel Begunkov asml.silence@gmail.com Link: https://lore.kernel.org/r/7ccff36e1375f2b0ebf73d957f037b43becc0dde.161521280... Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Hanjun Guo guohanjun@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/io_uring.c | 59 +++++++++++++++++++++++++++++----------------------------- 1 file changed, 30 insertions(+), 29 deletions(-)
--- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -346,7 +346,8 @@ struct io_ring_ctx {
struct idr io_buffer_idr;
- struct idr personality_idr; + struct xarray personalities; + u32 pers_next;
struct { unsigned cached_cq_tail; @@ -1212,7 +1213,7 @@ static struct io_ring_ctx *io_ring_ctx_a init_completion(&ctx->ref_comp); init_completion(&ctx->sq_thread_comp); idr_init(&ctx->io_buffer_idr); - idr_init(&ctx->personality_idr); + xa_init_flags(&ctx->personalities, XA_FLAGS_ALLOC1); mutex_init(&ctx->uring_lock); init_waitqueue_head(&ctx->wait); spin_lock_init(&ctx->completion_lock); @@ -6629,7 +6630,7 @@ static int io_init_req(struct io_ring_ct if (id) { struct io_identity *iod;
- iod = idr_find(&ctx->personality_idr, id); + iod = xa_load(&ctx->personalities, id); if (unlikely(!iod)) return -EINVAL; refcount_inc(&iod->count); @@ -8445,7 +8446,6 @@ static void io_ring_ctx_free(struct io_r io_sqe_files_unregister(ctx); io_eventfd_unregister(ctx); io_destroy_buffers(ctx); - idr_destroy(&ctx->personality_idr);
#if defined(CONFIG_UNIX) if (ctx->ring_sock) { @@ -8509,7 +8509,7 @@ static int io_unregister_personality(str { struct io_identity *iod;
- iod = idr_remove(&ctx->personality_idr, id); + iod = xa_erase(&ctx->personalities, id); if (iod) { put_cred(iod->creds); if (refcount_dec_and_test(&iod->count)) @@ -8520,14 +8520,6 @@ static int io_unregister_personality(str return -EINVAL; }
-static int io_remove_personalities(int id, void *p, void *data) -{ - struct io_ring_ctx *ctx = data; - - io_unregister_personality(ctx, id); - return 0; -} - static void io_ring_exit_work(struct work_struct *work) { struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx, @@ -8554,6 +8546,9 @@ static bool io_cancel_ctx_cb(struct io_w
static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx) { + unsigned long index; + struct io_identify *iod; + mutex_lock(&ctx->uring_lock); percpu_ref_kill(&ctx->refs); /* if force is set, the ring is going away. always drop after that */ @@ -8574,7 +8569,8 @@ static void io_ring_ctx_wait_and_kill(st
/* if we failed setting up the ctx, we might not have any rings */ io_iopoll_try_reap_events(ctx); - idr_for_each(&ctx->personality_idr, io_remove_personalities, ctx); + xa_for_each(&ctx->personalities, index, iod) + io_unregister_personality(ctx, index);
/* * Do this upfront, so we won't have a grace period where the ring @@ -9137,11 +9133,10 @@ out_fput: }
#ifdef CONFIG_PROC_FS -static int io_uring_show_cred(int id, void *p, void *data) +static int io_uring_show_cred(struct seq_file *m, unsigned int id, + const struct io_identity *iod) { - struct io_identity *iod = p; const struct cred *cred = iod->creds; - struct seq_file *m = data; struct user_namespace *uns = seq_user_ns(m); struct group_info *gi; kernel_cap_t cap; @@ -9209,9 +9204,13 @@ static void __io_uring_show_fdinfo(struc seq_printf(m, "%5u: 0x%llx/%u\n", i, buf->ubuf, (unsigned int) buf->len); } - if (has_lock && !idr_is_empty(&ctx->personality_idr)) { + if (has_lock && !xa_empty(&ctx->personalities)) { + unsigned long index; + const struct io_identity *iod; + seq_printf(m, "Personalities:\n"); - idr_for_each(&ctx->personality_idr, io_uring_show_cred, m); + xa_for_each(&ctx->personalities, index, iod) + io_uring_show_cred(m, index, iod); } seq_printf(m, "PollList:\n"); spin_lock_irq(&ctx->completion_lock); @@ -9597,21 +9596,23 @@ out:
static int io_register_personality(struct io_ring_ctx *ctx) { - struct io_identity *id; + struct io_identity *iod; + u32 id; int ret;
- id = kmalloc(sizeof(*id), GFP_KERNEL); - if (unlikely(!id)) + iod = kmalloc(sizeof(*iod), GFP_KERNEL); + if (unlikely(!iod)) return -ENOMEM;
- io_init_identity(id); - id->creds = get_current_cred(); + io_init_identity(iod); + iod->creds = get_current_cred();
- ret = idr_alloc_cyclic(&ctx->personality_idr, id, 1, USHRT_MAX, GFP_KERNEL); - if (ret < 0) { - put_cred(id->creds); - kfree(id); - } + ret = xa_alloc_cyclic(&ctx->personalities, &id, (void *)iod, + XA_LIMIT(0, USHRT_MAX), &ctx->pers_next, GFP_KERNEL); + if (!ret) + return id; + put_cred(iod->creds); + kfree(iod); return ret; }