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mm/mmap: fix memory leak in mmap_region()

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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@huawei.com
Fixes: d4af56c5c7 ("mm: start tracking VMAs with maple tree")
Fixes: c462ac288f ("mm: Introduce arch_validate_flags()")
Signed-off-by: Li Zetao <lizetao1@huawei.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Li Zetao 2022-10-28 15:37:17 +08:00 • committed by Andrew Morton
parent 8625147caf
commit cc674ab3c0
1 changed files with 5 additions and 1 deletions
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6
mm/mmap.c
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@ -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);