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btrfs: free the allocated memory if btrfs_alloc_page_array() fails

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[BUG]
If btrfs_alloc_page_array() fail to allocate all pages but part of the
slots, then the partially allocated pages would be leaked in function
btrfs_submit_compressed_read().

[CAUSE]
As explicitly stated, if btrfs_alloc_page_array() returned -ENOMEM,
caller is responsible to free the partially allocated pages.

For the existing call sites, most of them are fine:

- btrfs_raid_bio::stripe_pages
  Handled by free_raid_bio().

- extent_buffer::pages[]
  Handled btrfs_release_extent_buffer_pages().

- scrub_stripe::pages[]
  Handled by release_scrub_stripe().

But there is one exception in btrfs_submit_compressed_read(), if
btrfs_alloc_page_array() failed, we didn't cleanup the array and freed
the array pointer directly.

Initially there is still the error handling in commit dd137dd1f2
("btrfs: factor out allocating an array of pages"), but later in commit
544fe4a903 ("btrfs: embed a btrfs_bio into struct compressed_bio"),
the error handling is removed, leading to the possible memory leak.

[FIX]
This patch would add back the error handling first, then to prevent such
situation from happening again, also
Make btrfs_alloc_page_array() to free the allocated pages as a extra
safety net, then we don't need to add the error handling to
btrfs_submit_compressed_read().

Fixes: 544fe4a903 ("btrfs: embed a btrfs_bio into struct compressed_bio")
CC: stable@vger.kernel.org # 6.4+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2023-11-24 14:53:50 +10:30 committed by David Sterba
parent 5de0434bc0
commit 94dbf7c087
1 changed files with 8 additions and 3 deletions
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11
fs/btrfs/extent_io.c
View file

@ -674,8 +674,8 @@ static void end_bio_extent_readpage(struct btrfs_bio *bbio)
* the array will be skipped
*
* Return: 0 if all pages were able to be allocated;
* -ENOMEM otherwise, and the caller is responsible for freeing all
* non-null page pointers in the array.
* -ENOMEM otherwise, the partially allocated pages would be freed and
* the array slots zeroed
*/
int btrfs_alloc_page_array(unsigned int nr_pages, struct page **page_array)
{
@ -694,8 +694,13 @@ int btrfs_alloc_page_array(unsigned int nr_pages, struct page **page_array)
* though alloc_pages_bulk_array() falls back to alloc_page()
* if it could not bulk-allocate. So we must be out of memory.
*/
if (allocated == last)
if (allocated == last) {
for (int i = 0; i < allocated; i++) {
__free_page(page_array[i]);
page_array[i] = NULL;
}
return -ENOMEM;
}
memalloc_retry_wait(GFP_NOFS);
}