The patch titled
Subject: mm/mmap: fix memory leak in mmap_region()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-mmap-fix-memory-leak-in-mmap_region.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mmap-fix-memory-leak-in-mmap_region.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Li Zetao <lizetao1@xxxxxxxxxx>
Subject: mm/mmap: fix memory leak in mmap_region()
Date: Fri, 28 Oct 2022 15:37:17 +0800
There is a memory leak reported by kmemleak:
unreferenced object 0xffff88817231ce40 (size 224):
comm "mount.cifs", pid 19308, jiffies 4295917571 (age 405.880s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
60 c0 b2 00 81 88 ff ff 98 83 01 42 81 88 ff ff `..........B....
backtrace:
[<ffffffff81936171>] __alloc_file+0x21/0x250
[<ffffffff81937051>] alloc_empty_file+0x41/0xf0
[<ffffffff81937159>] alloc_file+0x59/0x710
[<ffffffff81937964>] alloc_file_pseudo+0x154/0x210
[<ffffffff81741dbf>] __shmem_file_setup+0xff/0x2a0
[<ffffffff817502cd>] shmem_zero_setup+0x8d/0x160
[<ffffffff817cc1d5>] mmap_region+0x1075/0x19d0
[<ffffffff817cd257>] do_mmap+0x727/0x1110
[<ffffffff817518b2>] vm_mmap_pgoff+0x112/0x1e0
[<ffffffff83adf955>] do_syscall_64+0x35/0x80
[<ffffffff83c0006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
The root cause was traced to an error handing path in mmap_region() when
arch_validate_flags() or mas_preallocate() fails. In the shared anonymous
mapping sence, vma will be setuped and mapped with a new shared anonymous
file via shmem_zero_setup(). So in this case, the file resource needs to
be released.
Fix it by calling fput(vma->vm_file) and unmap_region() when
arch_validate_flags() or mas_preallocate() returns an error in the shared
anonymous mapping sence.
Link: https://lkml.kernel.org/r/20221028073717.1179380-1-lizetao1@xxxxxxxxxx
Fixes: d4af56c5c7c6 ("mm: start tracking VMAs with maple tree")
Fixes: c462ac288f2c ("mm: Introduce arch_validate_flags()")
Signed-off-by: Li Zetao <lizetao1@xxxxxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/mmap.c~mm-mmap-fix-memory-leak-in-mmap_region
+++ a/mm/mmap.c
@@ -2674,6 +2674,8 @@ cannot_expand:
error = -EINVAL;
if (file)
goto close_and_free_vma;
+ else if (vma->vm_file)
+ goto unmap_and_free_vma;
else
goto free_vma;
}
@@ -2682,6 +2684,8 @@ cannot_expand:
error = -ENOMEM;
if (file)
goto close_and_free_vma;
+ else if (vma->vm_file)
+ goto unmap_and_free_vma;
else
goto free_vma;
}
@@ -2751,7 +2755,7 @@ unmap_and_free_vma:
/* Undo any partial mapping done by a device driver. */
unmap_region(mm, mas.tree, vma, prev, next, vma->vm_start, vma->vm_end);
- if (vm_flags & VM_SHARED)
+ if (file && (vm_flags & VM_SHARED))
mapping_unmap_writable(file->f_mapping);
free_vma:
vm_area_free(vma);
_
Patches currently in -mm which might be from lizetao1@xxxxxxxxxx are
mm-mmap-fix-memory-leak-in-mmap_region.patch
