6.6-stable review patch. If anyone has any objections, please let me know.
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From: Qu Wenruo wqu@suse.com
commit 94dbf7c0871f7ae6349ba4b0341ce8f5f98a071d upstream.
[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 dd137dd1f2d7 ("btrfs: factor out allocating an array of pages"), but later in commit 544fe4a903ce ("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: 544fe4a903ce ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/extent_io.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
--- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -675,8 +675,8 @@ static void end_bio_extent_readpage(stru * 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) { @@ -695,8 +695,13 @@ int btrfs_alloc_page_array(unsigned int * 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); }