aio: sanitize the limit checking in io_submit(2)

as it is, the logics in native io_submit(2) is "if asked for more than LONG_MAX/sizeof(pointer) iocbs to submit, don't bother with more than LONG_MAX/sizeof(pointer)" (i.e. 512M requests on 32bit and 1E requests on 64bit) while compat io_submit(2) goes with "stop after the first PAGE_SIZE/sizeof(pointer) iocbs", i.e. 1K or so. Which is * inconsistent * *way* too much in native case * possibly too little in compat one and * wrong anyway, since the natural point where we ought to stop bothering is ctx->nr_events Reviewed-by: Christoph Hellwig <[email protected]> Signed-off-by: Al Viro <[email protected]>
michelpromonet · May 30, 2018 · 1da9277 · 1da9277
1 parent 67ba049
commit 1da9277
Showing 1 changed file with 6 additions and 8 deletions.
diff --git a/fs/aio.c b/fs/aio.c
@@ -1841,15 +1841,15 @@ SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
 	if (unlikely(nr < 0))
 		return -EINVAL;
 
-	if (unlikely(nr > LONG_MAX/sizeof(*iocbpp)))
-		nr = LONG_MAX/sizeof(*iocbpp);
-
 	ctx = lookup_ioctx(ctx_id);
 	if (unlikely(!ctx)) {
 		pr_debug("EINVAL: invalid context id\n");
 		return -EINVAL;
 	}
 
+	if (nr > ctx->nr_events)
+		nr = ctx->nr_events;
+
 	blk_start_plug(&plug);
 	for (i = 0; i < nr; i++) {
 		struct iocb __user *user_iocb;
@@ -1870,8 +1870,6 @@ SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
 }
 
 #ifdef CONFIG_COMPAT
-#define MAX_AIO_SUBMITS 	(PAGE_SIZE/sizeof(struct iocb *))
-
 COMPAT_SYSCALL_DEFINE3(io_submit, compat_aio_context_t, ctx_id,
 		       int, nr, compat_uptr_t __user *, iocbpp)
 {
@@ -1883,15 +1881,15 @@ COMPAT_SYSCALL_DEFINE3(io_submit, compat_aio_context_t, ctx_id,
 	if (unlikely(nr < 0))
 		return -EINVAL;
 
-	if (nr > MAX_AIO_SUBMITS)
-		nr = MAX_AIO_SUBMITS;
-
 	ctx = lookup_ioctx(ctx_id);
 	if (unlikely(!ctx)) {
 		pr_debug("EINVAL: invalid context id\n");
 		return -EINVAL;
 	}
 
+	if (nr > ctx->nr_events)
+		nr = ctx->nr_events;
+
 	blk_start_plug(&plug);
 	for (i = 0; i < nr; i++) {
 		compat_uptr_t user_iocb;