FAILED: patch "[PATCH] misc: fastrpc: Add missing lock before accessing find_vma()" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f9a470db2736b01538ad193c316eb3f26be37d58 Mon Sep 17 00:00:00 2001
From: Srinivas Kandagatla <[email protected]>
Date: Wed, 22 Sep 2021 16:43:26 +0100
Subject: [PATCH] misc: fastrpc: Add missing lock before accessing find_vma()

fastrpc driver is using find_vma() without any protection, as a result we see below warning due to recent patch 5b78ed24e8ec ("mm/pagemap: add mmap_assert_locked() annotations to find_vma*()") which added mmap_assert_locked() in find_vma() function.

This bug went un-noticed in previous versions. Fix this issue by adding required protection while calling find_vma().

CPU: 0 PID: 209746 Comm: benchmark_model Not tainted 5.15.0-rc2-00445-ge14fe2bf817a-dirty #969
Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : find_vma+0x64/0xd0
lr : find_vma+0x60/0xd0

sp : ffff8000158ebc40
...

Call trace:
 find_vma+0x64/0xd0
 fastrpc_internal_invoke+0x570/0xda8
 fastrpc_device_ioctl+0x3e0/0x928
 __arm64_sys_ioctl+0xac/0xf0
 invoke_syscall+0x44/0x100
 el0_svc_common.constprop.3+0x70/0xf8
 do_el0_svc+0x24/0x88
 el0_svc+0x3c/0x138
 el0t_64_sync_handler+0x90/0xb8
 el0t_64_sync+0x180/0x184

index beda610e6b30..ad6ced454655 100644
@@ -814,10 +814,12 @@ static int fastrpc_get_args(u32 kernel, struct fastrpc_invoke_ctx *ctx)
 			rpra[i].pv = (u64) ctx->args[i].ptr;
 			pages[i].addr = ctx->maps[i]->phys;
 
+			mmap_read_lock(current->mm);
 			vma = find_vma(current->mm, ctx->args[i].ptr);
 			if (vma)
 				pages[i].addr += ctx->args[i].ptr -
 						 vma->vm_start;
+			mmap_read_unlock(current->mm);
 
 			pg_start = (ctx->args[i].ptr & PAGE_MASK) >> PAGE_SHIFT;
 			pg_end = ((ctx->args[i].ptr + len - 1) & PAGE_MASK) >>