From: "Matthew Wilcox (Oracle)"
mainline inclusion
from mainline-v5.12-rc3
commit 61cf93700fe6359552848ed5e3becba6cd760efa
category: bugfix
issue: #I3ZXZF
CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
---------------------------
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
Signed-off-by: Matthew Wilcox (Oracle)
[Pavel: rebased (creds load was moved into io_init_req())]
Signed-off-by: Pavel Begunkov
Link: https://lore.kernel.org/r/7ccff36e1375f2b0ebf73d957f037b43becc0dde.161521280...
Signed-off-by: Jens Axboe
Conflicts:
fs/io_uring.c
Signed-off-by: yangerkun
Reviewed-by: zhangyi (F)
Signed-off-by: Chen Jun
Signed-off-by: Yu Changchun
---
fs/io_uring.c | 59 ++++++++++++++++++++++++++-------------------------
1 file changed, 30 insertions(+), 29 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 706ecf330edc..01e1108c0d87 100644
--- 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_alloc(struct io_uring_params *p)
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_ctx *ctx, struct io_kiocb *req,
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_ring_ctx *ctx)
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(struct io_ring_ctx *ctx, unsigned id)
{
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(struct io_ring_ctx *ctx, unsigned id)
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_wq_work *work, void *data)
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(struct io_ring_ctx *ctx)
/* 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 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
}
#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(struct io_ring_ctx *ctx, struct seq_file *m)
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 @@ static int io_probe(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args)
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;
}
--
2.22.0
