mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/
synced 2026-11-10 20:48:12 +00:00
8f3901fbb4
Resend: previous attempt was rejected by vger for containing HTML.
==================================================================
ext4_mark_group_bitmap_corrupted() already treats a NULL return from
ext4_get_group_info() as "nothing to do", but ext4_get_group_info()
indexes s_group_info without checking whether the array exists.
During mount, fast-commit replay runs inside jbd2_journal_load() from
ext4_load_and_init_journal(), which is before ext4_mb_init() allocates
s_group_info. Replaying an FC UNLINK for an inode whose bitmap bit is
already clear takes:
ext4_fc_replay_unlink -> iput -> ext4_evict_inode -> ext4_free_inode
-> ext4_mark_group_bitmap_corrupted -> ext4_get_group_info
and faults on the NULL s_group_info base. Userspace only mounts a dirty
ext4 image; this is a supported recovery path.
Return NULL when s_group_info (or the per-block grp_info row) is unset
so the existing caller check is effective during early mount.
Tested on Linux v6.6.145 KASAN: crafted FC-unlink image previously
triggered KASAN null-ptr-deref / panic in ext4_get_group_info; with this
patch, mount succeeds (EXT4 "bit already cleared" may still log). Also
observed on v6.6.144; still present on torvalds/linux as of
f5098b6bae (2026-07-26).
A self-contained Docker/QEMU reproducer (craft + mount + patch verify) is
available on request.
Signed-off-by: Yu Junzhe <junzheyu1@gmail.com>
Link: https://patch.msgid.link/65c955b0-716b-4599-b925-59c2782e38b4@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
1007 lines
29 KiB
1007 lines
29 KiB