dm: always update the array size in realloc_argv on success

JIRA: https://issues.redhat.com/browse/RHEL-92761
Upstream Status: kernel/git/torvalds/linux.git

commit 5a2a6c4
Author: Benjamin Marzinski <bmarzins@redhat.com>
Date:   Tue Apr 15 00:17:16 2025 -0400

    dm: always update the array size in realloc_argv on success

    realloc_argv() was only updating the array size if it was called with
    old_argv already allocated. The first time it was called to create an
    argv array, it would allocate the array but return the array size as
    zero. dm_split_args() would think that it couldn't store any arguments
    in the array and would call realloc_argv() again, causing it to
    reallocate the initial slots (this time using GPF_KERNEL) and finally
    return a size. Aside from being wasteful, this could cause deadlocks on
    targets that need to process messages without starting new IO. Instead,
    realloc_argv should always update the allocated array size on success.

    Fixes: a065192 ("dm table: don't copy from a NULL pointer in realloc_argv()")
    Cc: stable@vger.kernel.org
    Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
    Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>

Author: bmarzins

drivers/md/dm-table.c

@@ -523,9 +523,10 @@ static char **realloc_argv(unsigned int *size, char **old_argv)
 		gfp = GFP_NOIO;
 	}
 	argv = kmalloc_array(new_size, sizeof(*argv), gfp);
-	if (argv && old_argv) {
-		memcpy(argv, old_argv, *size * sizeof(*argv));
+	if (argv) {
 		*size = new_size;
+		if (old_argv)
+			memcpy(argv, old_argv, *size * sizeof(*argv));
 	}
 
 	kfree(old_argv);