[PATCH 5.11 276/329] f2fs: compress: fix race condition of overwrite vs truncate
From: Greg Kroah-Hartman
Date: Mon May 17 2021 - 11:59:20 EST
From: Chao Yu <yuchao0@xxxxxxxxxx>
[ Upstream commit a949dc5f2c5cfe0c910b664650f45371254c0744 ]
pos_fsstress testcase complains a panic as belew:
------------[ cut here ]------------
kernel BUG at fs/f2fs/compress.c:1082!
invalid opcode: 0000 [#1] SMP PTI
CPU: 4 PID: 2753477 Comm: kworker/u16:2 Tainted: G OE 5.12.0-rc1-custom #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
Workqueue: writeback wb_workfn (flush-252:16)
RIP: 0010:prepare_compress_overwrite+0x4c0/0x760 [f2fs]
Call Trace:
f2fs_prepare_compress_overwrite+0x5f/0x80 [f2fs]
f2fs_write_cache_pages+0x468/0x8a0 [f2fs]
f2fs_write_data_pages+0x2a4/0x2f0 [f2fs]
do_writepages+0x38/0xc0
__writeback_single_inode+0x44/0x2a0
writeback_sb_inodes+0x223/0x4d0
__writeback_inodes_wb+0x56/0xf0
wb_writeback+0x1dd/0x290
wb_workfn+0x309/0x500
process_one_work+0x220/0x3c0
worker_thread+0x53/0x420
kthread+0x12f/0x150
ret_from_fork+0x22/0x30
The root cause is truncate() may race with overwrite as below,
so that one reference count left in page can not guarantee the
page attaching in mapping tree all the time, after truncation,
later find_lock_page() may return NULL pointer.
- prepare_compress_overwrite
- f2fs_pagecache_get_page
- unlock_page
- f2fs_setattr
- truncate_setsize
- truncate_inode_page
- delete_from_page_cache
- find_lock_page
Fix this by avoiding referencing updated page.
Fixes: 4c8ff7095bef ("f2fs: support data compression")
Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/f2fs/compress.c | 35 ++++++++++++-----------------------
1 file changed, 12 insertions(+), 23 deletions(-)
diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index ac12adc17f5e..8093d06116b4 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -123,19 +123,6 @@ static void f2fs_unlock_rpages(struct compress_ctx *cc, int len)
f2fs_drop_rpages(cc, len, true);
}
-static void f2fs_put_rpages_mapping(struct address_space *mapping,
- pgoff_t start, int len)
-{
- int i;
-
- for (i = 0; i < len; i++) {
- struct page *page = find_get_page(mapping, start + i);
-
- put_page(page);
- put_page(page);
- }
-}
-
static void f2fs_put_rpages_wbc(struct compress_ctx *cc,
struct writeback_control *wbc, bool redirty, int unlock)
{
@@ -1008,7 +995,7 @@ static int prepare_compress_overwrite(struct compress_ctx *cc,
}
if (PageUptodate(page))
- unlock_page(page);
+ f2fs_put_page(page, 1);
else
f2fs_compress_ctx_add_page(cc, page);
}
@@ -1018,32 +1005,34 @@ static int prepare_compress_overwrite(struct compress_ctx *cc,
ret = f2fs_read_multi_pages(cc, &bio, cc->cluster_size,
&last_block_in_bio, false, true);
+ f2fs_put_rpages(cc);
f2fs_destroy_compress_ctx(cc);
if (ret)
- goto release_pages;
+ goto out;
if (bio)
f2fs_submit_bio(sbi, bio, DATA);
ret = f2fs_init_compress_ctx(cc);
if (ret)
- goto release_pages;
+ goto out;
}
for (i = 0; i < cc->cluster_size; i++) {
f2fs_bug_on(sbi, cc->rpages[i]);
page = find_lock_page(mapping, start_idx + i);
- f2fs_bug_on(sbi, !page);
+ if (!page) {
+ /* page can be truncated */
+ goto release_and_retry;
+ }
f2fs_wait_on_page_writeback(page, DATA, true, true);
-
f2fs_compress_ctx_add_page(cc, page);
- f2fs_put_page(page, 0);
if (!PageUptodate(page)) {
+release_and_retry:
+ f2fs_put_rpages(cc);
f2fs_unlock_rpages(cc, i + 1);
- f2fs_put_rpages_mapping(mapping, start_idx,
- cc->cluster_size);
f2fs_destroy_compress_ctx(cc);
goto retry;
}
@@ -1075,10 +1064,10 @@ static int prepare_compress_overwrite(struct compress_ctx *cc,
}
unlock_pages:
+ f2fs_put_rpages(cc);
f2fs_unlock_rpages(cc, i);
-release_pages:
- f2fs_put_rpages_mapping(mapping, start_idx, i);
f2fs_destroy_compress_ctx(cc);
+out:
return ret;
}
--
2.30.2