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authorBaokun Li <[email protected]>2024-08-22 10:35:26 +0800
committerTheodore Ts'o <[email protected]>2024-09-03 22:12:16 -0400
commita164f3a432aae62ca23d03e6d926b122ee5b860d (patch)
treec2cead40f4ea96061bd3b4a9cdf8c08c7510466d
parent5b4b2dcace35f618fe361a87bae6f0d13af31bc1 (diff)
ext4: aovid use-after-free in ext4_ext_insert_extent()
As Ojaswin mentioned in Link, in ext4_ext_insert_extent(), if the path is reallocated in ext4_ext_create_new_leaf(), we'll use the stale path and cause UAF. Below is a sample trace with dummy values: ext4_ext_insert_extent path = *ppath = 2000 ext4_ext_create_new_leaf(ppath) ext4_find_extent(ppath) path = *ppath = 2000 if (depth > path[0].p_maxdepth) kfree(path = 2000); *ppath = path = NULL; path = kcalloc() = 3000 *ppath = 3000; return path; /* here path is still 2000, UAF! */ eh = path[depth].p_hdr ================================================================== BUG: KASAN: slab-use-after-free in ext4_ext_insert_extent+0x26d4/0x3330 Read of size 8 at addr ffff8881027bf7d0 by task kworker/u36:1/179 CPU: 3 UID: 0 PID: 179 Comm: kworker/u6:1 Not tainted 6.11.0-rc2-dirty #866 Call Trace: <TASK> ext4_ext_insert_extent+0x26d4/0x3330 ext4_ext_map_blocks+0xe22/0x2d40 ext4_map_blocks+0x71e/0x1700 ext4_do_writepages+0x1290/0x2800 [...] Allocated by task 179: ext4_find_extent+0x81c/0x1f70 ext4_ext_map_blocks+0x146/0x2d40 ext4_map_blocks+0x71e/0x1700 ext4_do_writepages+0x1290/0x2800 ext4_writepages+0x26d/0x4e0 do_writepages+0x175/0x700 [...] Freed by task 179: kfree+0xcb/0x240 ext4_find_extent+0x7c0/0x1f70 ext4_ext_insert_extent+0xa26/0x3330 ext4_ext_map_blocks+0xe22/0x2d40 ext4_map_blocks+0x71e/0x1700 ext4_do_writepages+0x1290/0x2800 ext4_writepages+0x26d/0x4e0 do_writepages+0x175/0x700 [...] ================================================================== So use *ppath to update the path to avoid the above problem. Reported-by: Ojaswin Mujoo <[email protected]> Closes: https://lore.kernel.org/r/[email protected] Fixes: 10809df84a4d ("ext4: teach ext4_ext_find_extent() to realloc path if necessary") Cc: [email protected] Signed-off-by: Baokun Li <[email protected]> Reviewed-by: Jan Kara <[email protected]> Link: https://patch.msgid.link/[email protected] Signed-off-by: Theodore Ts'o <[email protected]>
-rw-r--r--fs/ext4/extents.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index c8e7676f6af9..b431fcfb6ef8 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2116,6 +2116,7 @@ prepend:
ppath, newext);
if (err)
goto cleanup;
+ path = *ppath;
depth = ext_depth(inode);
eh = path[depth].p_hdr;