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Message-ID: <ggvucjixgiuelt6vjz6oawgyobmzrhifaozqqvupwfso65ia7c@bauvfqtvq6lv>
Date: Fri, 18 Oct 2024 13:49:06 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Roberto Sassu <roberto.sassu@...weicloud.com>
Cc: Paul Moore <paul@...l-moore.com>, ebpqwerty472123@...il.com,
kirill.shutemov@...ux.intel.com, zohar@...ux.ibm.com, dmitry.kasatkin@...il.com,
eric.snowberg@...cle.com, jmorris@...ei.org, serge@...lyn.com,
linux-integrity@...r.kernel.org, linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, bpf@...r.kernel.org, Roberto Sassu <roberto.sassu@...wei.com>,
linux-mm@...ck.org, akpm@...ux-foundation.org, vbabka@...e.cz,
lorenzo.stoakes@...cle.com, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/3] ima: Remove inode lock
On Fri, Oct 18, 2024 at 11:24:06AM +0200, Roberto Sassu wrote:
> Probably it is hard, @Kirill would there be any way to safely move
> security_mmap_file() out of the mmap_lock lock?
What about something like this (untested):
diff --git a/mm/mmap.c b/mm/mmap.c
index dd4b35a25aeb..03473e77d356 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1646,6 +1646,26 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
if (pgoff + (size >> PAGE_SHIFT) < pgoff)
return ret;
+ if (mmap_read_lock_killable(mm))
+ return -EINTR;
+
+ vma = vma_lookup(mm, start);
+
+ if (!vma || !(vma->vm_flags & VM_SHARED)) {
+ mmap_read_unlock(mm);
+ return -EINVAL;
+ }
+
+ file = get_file(vma->vm_file);
+
+ mmap_read_unlock(mm);
+
+ ret = security_mmap_file(vma->vm_file, prot, flags);
+ if (ret) {
+ fput(file);
+ return ret;
+ }
+
if (mmap_write_lock_killable(mm))
return -EINTR;
@@ -1654,6 +1674,9 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
if (!vma || !(vma->vm_flags & VM_SHARED))
goto out;
+ if (vma->vm_file != file)
+ goto out;
+
if (start + size > vma->vm_end) {
VMA_ITERATOR(vmi, mm, vma->vm_end);
struct vm_area_struct *next, *prev = vma;
@@ -1688,16 +1711,11 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
if (vma->vm_flags & VM_LOCKED)
flags |= MAP_LOCKED;
- file = get_file(vma->vm_file);
- ret = security_mmap_file(vma->vm_file, prot, flags);
- if (ret)
- goto out_fput;
ret = do_mmap(vma->vm_file, start, size,
prot, flags, 0, pgoff, &populate, NULL);
-out_fput:
- fput(file);
out:
mmap_write_unlock(mm);
+ fput(file);
if (populate)
mm_populate(ret, populate);
if (!IS_ERR_VALUE(ret))
--
Kiryl Shutsemau / Kirill A. Shutemov
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