[RFC] Patch for null-ptr-deref read in io_uring_create 5.11.12

[Palash Oswal <hello@oswalpalash.com>]

Hello,

I have been trying to decipher a bug that my local syzkaller instance
discovered in the v5.11.12 stable tree. I have more details in [1].
Could someone please review.

[1] https://oswalpalash.com/exploring-null-ptr-deref-io-uring-submit/
Signed-off-by: Palash Oswal <hello@oswalpalash.com>
---
 fs/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 8b4213de9e08..00b35079b91a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8995,7 +8995,7 @@ static void io_disable_sqo_submit(struct io_ring_ctx *ctx)
 {
     mutex_lock(&ctx->uring_lock);
     ctx->sqo_dead = 1;
-    if (ctx->flags & IORING_SETUP_R_DISABLED)
+    if (ctx->flags & IORING_SETUP_R_DISABLED && ctx->sq_data)
         io_sq_offload_start(ctx);
     mutex_unlock(&ctx->uring_lock);

-- 
2.27.0