[PATCH 6.1 298/312] erofs: fix PSI memstall accounting

Greg Kroah-Hartman
2026-04-08T18:20:19Z

From: Gao Xiang <hsiangkao@linux.alibaba.com>

commit 1a2180f6859c73c674809f9f82e36c94084682ba upstream.

Max Kellermann recently reported psi_group_cpu.tasks[NR_MEMSTALL] is
incorrect in the 6.11.9 kernel.

The root cause appears to be that, since the problematic commit, bio
can be NULL, causing psi_memstall_leave() to be skipped in
z_erofs_submit_queue().

Reported-by: Max Kellermann <max.kellermann@ionos.com>
Closes: https://lore.kernel.org/r/CAKPOu+8tvSowiJADW2RuKyofL_CSkm_SuyZA7ME5vMLWmL6pqw@mail.gmail.com
Fixes: 9e2f9d34dd12 ("erofs: handle overlapped pclusters out of crafted images properly")
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20241127085236.3538334-1-hsiangkao@linux.alibaba.com
Signed-off-by: Alexey Panov <apanov@astralinux.ru>
Link: https://lore.kernel.org/r/20250304110558.8315-3-apanov@astralinux.ru
Link: https://lore.kernel.org/r/20250304110558.8315-1-apanov@astralinux.ru
[ Gao Xiang: re-address the previous Alexey's backport. ]
CVE: CVE-2024-47736
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/erofs/zdata.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -1574,11 +1574,10 @@ drain_io:
move_to_bypass_jobqueue(pcl, qtail, owned_head);
} while (owned_head != Z_EROFS_PCLUSTER_TAIL);

- if (bio) {
+ if (bio)
submit_bio(bio);
- if (memstall)
- psi_memstall_leave(&pflags);
- }
+ if (memstall)
+ psi_memstall_leave(&pflags);

/*
* although background is preferred, no one is pending for submission.