From c1a55f76894e45610a338d013cacd71e512a8d56 Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Thu, 4 Jul 2024 16:11:20 +0100 Subject: [PATCH] btrfs: fix extent map use-after-free when adding pages to compressed bio BugLink: https://bugs.launchpad.net/bugs/2083196 commit 8e7860543a94784d744c7ce34b78a2e11beefa5c upstream. At add_ra_bio_pages() we are accessing the extent map to calculate 'add_size' after we dropped our reference on the extent map, resulting in a use-after-free. Fix this by computing 'add_size' before dropping our extent map reference. Reported-by: syzbot+853d80cba98ce1157ae6@syzkaller.appspotmail.com Link: https://lore.kernel.org/linux-btrfs/000000000000038144061c6d18f2@google.com/ Fixes: 6a4049102055 ("btrfs: subpage: make add_ra_bio_pages() compatible") CC: stable@vger.kernel.org # 6.1+ Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman Signed-off-by: Portia Stephens Signed-off-by: Roxana Nicolescu --- fs/btrfs/compression.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 0041613a36ae..1ff6745f9110 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -515,6 +515,7 @@ static noinline int add_ra_bio_pages(struct inode *inode, put_page(page); break; } + add_size = min(em->start + em->len, page_end + 1) - cur; free_extent_map(em); if (page->index == end_index) { @@ -527,7 +528,6 @@ static noinline int add_ra_bio_pages(struct inode *inode, } } - add_size = min(em->start + em->len, page_end + 1) - cur; ret = bio_add_page(orig_bio, page, add_size, offset_in_page(cur)); if (ret != add_size) { unlock_extent(tree, cur, page_end, NULL);