FAILED: patch "[PATCH] btrfs: fix extent map use-after-free when adding pages to" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 8e7860543a94784d744c7ce34b78a2e11beefa5c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024072924-overact-drainable-8abb@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

8e7860543a94 ("btrfs: fix extent map use-after-free when adding pages to compressed bio")
b7d463a1d125 ("btrfs: store a pointer to the original btrfs_bio in struct compressed_bio")
690834e47cf7 ("btrfs: pass a btrfs_bio to btrfs_submit_compressed_read")
7edb9a3e7200 ("btrfs: move zero filling of compressed read bios into common code")
32586c5bca72 ("btrfs: factor out a btrfs_free_compressed_pages helper")
10e924bc320a ("btrfs: factor out a btrfs_add_compressed_bio_pages helper")
d7294e4deeb9 ("btrfs: use the bbio file offset in add_ra_bio_pages")
e7aff33e3161 ("btrfs: use the bbio file offset in btrfs_submit_compressed_read")
798c9fc74d03 ("btrfs: remove redundant free_extent_map in btrfs_submit_compressed_read")
544fe4a903ce ("btrfs: embed a btrfs_bio into struct compressed_bio")
d5e4377d5051 ("btrfs: split zone append bios in btrfs_submit_bio")
35a8d7da3ca8 ("btrfs: remove now spurious bio submission helpers")
285599b6fe15 ("btrfs: remove the fs_info argument to btrfs_submit_bio")
48253076c3a9 ("btrfs: open code submit_encoded_read_bio")
30493ff49f81 ("btrfs: remove stripe boundary calculation for compressed I/O")
2380220e1e13 ("btrfs: remove stripe boundary calculation for buffered I/O")
67d669825090 ("btrfs: pass the iomap bio to btrfs_submit_bio")
852eee62d31a ("btrfs: allow btrfs_submit_bio to split bios")
69ccf3f4244a ("btrfs: handle recording of zoned writes in the storage layer")
f8a53bb58ec7 ("btrfs: handle checksum generation in the storage layer")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8e7860543a94784d744c7ce34b78a2e11beefa5c Mon Sep 17 00:00:00 2001
From: Filipe Manana <fdmanana@suse.com>
Date: Thu, 4 Jul 2024 16:11:20 +0100
Subject: [PATCH] btrfs: fix extent map use-after-free when adding pages to
 compressed bio

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 <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index a149f3659b15..a8e2c461aff7 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);