The patch below does not apply to the 4.19-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-4.19.y git checkout FETCH_HEAD git cherry-pick -x 5b4b2dcace35f618fe361a87bae6f0d13af31bc1 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024100721-bouncy-retreat-a211@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

5b4b2dcace35 ("ext4: update orig_path in ext4_find_extent()") c26ab35702f8 ("ext4: fix slab-use-after-free in ext4_split_extent_at()") 082cd4ec240b ("ext4: fix bug on in ext4_es_cache_extent as ext4_split_extent_at failed")

thanks,

greg k-h

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

From 5b4b2dcace35f618fe361a87bae6f0d13af31bc1 Mon Sep 17 00:00:00 2001 From: Baokun Li libaokun1@huawei.com Date: Thu, 22 Aug 2024 10:35:25 +0800 Subject: [PATCH] ext4: update orig_path in ext4_find_extent()

In ext4_find_extent(), if the path is not big enough, we free it and set *orig_path to NULL. But after reallocating and successfully initializing the path, we don't update *orig_path, in which case the caller gets a valid path but a NULL ppath, and this may cause a NULL pointer dereference or a path memory leak. For example:

ext4_split_extent path = *ppath = 2000 ext4_find_extent if (depth > path[0].p_maxdepth) kfree(path = 2000); *orig_path = path = NULL; path = kcalloc() = 3000 ext4_split_extent_at(*ppath = NULL) path = *ppath; ex = path[depth].p_ext; // NULL pointer dereference!

================================================================== BUG: kernel NULL pointer dereference, address: 0000000000000010 CPU: 6 UID: 0 PID: 576 Comm: fsstress Not tainted 6.11.0-rc2-dirty #847 RIP: 0010:ext4_split_extent_at+0x6d/0x560 Call Trace: <TASK> ext4_split_extent.isra.0+0xcb/0x1b0 ext4_ext_convert_to_initialized+0x168/0x6c0 ext4_ext_handle_unwritten_extents+0x325/0x4d0 ext4_ext_map_blocks+0x520/0xdb0 ext4_map_blocks+0x2b0/0x690 ext4_iomap_begin+0x20e/0x2c0 [...] ==================================================================

Therefore, *orig_path is updated when the extent lookup succeeds, so that the caller can safely use path or *ppath.

Fixes: 10809df84a4d ("ext4: teach ext4_ext_find_extent() to realloc path if necessary") Cc: stable@kernel.org Signed-off-by: Baokun Li libaokun1@huawei.com Reviewed-by: Jan Kara jack@suse.cz Link: https://patch.msgid.link/20240822023545.1994557-6-libaokun@huaweicloud.com Signed-off-by: Theodore Ts'o tytso@mit.edu

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index caef91356557..c8e7676f6af9 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -957,6 +957,8 @@ ext4_find_extent(struct inode *inode, ext4_lblk_t block,

ext4_ext_show_path(inode, path);

+ if (orig_path) + *orig_path = path; return path;

err: @@ -3268,7 +3270,6 @@ static int ext4_split_extent_at(handle_t *handle, } depth = ext_depth(inode); ex = path[depth].p_ext; - *ppath = path;

if (EXT4_EXT_MAY_ZEROOUT & split_flag) { if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) { diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c index 516897b0218e..228b56f7d047 100644 --- a/fs/ext4/move_extent.c +++ b/fs/ext4/move_extent.c @@ -36,7 +36,6 @@ get_ext_path(struct inode *inode, ext4_lblk_t lblock, *ppath = NULL; return -ENODATA; } - *ppath = path; return 0; }