Commit 62f63eea authored Mar 19, 2020 by Chao Yu Committed by Jaegeuk Kim Mar 30, 2020

f2fs: fix NULL pointer dereference in f2fs_write_begin()



BUG: kernel NULL pointer dereference, address: 0000000000000000
RIP: 0010:f2fs_write_begin+0x823/0xb90 [f2fs]
Call Trace:
 f2fs_quota_write+0x139/0x1d0 [f2fs]
 write_blk+0x36/0x80 [quota_tree]
 get_free_dqblk+0x42/0xa0 [quota_tree]
 do_insert_tree+0x235/0x4a0 [quota_tree]
 do_insert_tree+0x26e/0x4a0 [quota_tree]
 do_insert_tree+0x26e/0x4a0 [quota_tree]
 do_insert_tree+0x26e/0x4a0 [quota_tree]
 qtree_write_dquot+0x70/0x190 [quota_tree]
 v2_write_dquot+0x43/0x90 [quota_v2]
 dquot_acquire+0x77/0x100
 f2fs_dquot_acquire+0x2f/0x60 [f2fs]
 dqget+0x310/0x450
 dquot_transfer+0x7e/0x120
 f2fs_setattr+0x11a/0x4a0 [f2fs]
 notify_change+0x349/0x480
 chown_common+0x168/0x1c0
 do_fchownat+0xbc/0xf0
 __x64_sys_fchownat+0x20/0x30
 do_syscall_64+0x5f/0x220
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Passing fsdata parameter to .write_{begin,end} in f2fs_quota_write(),
so that if quota file is compressed one, we can avoid above NULL
pointer dereference when updating quota content.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

parent 8c7d4b57

fs/f2fs/super.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -1929,6 +1929,7 @@ static ssize_t f2fs_quota_write(struct super_block *sb, int type,
		int offset = off & (sb->s_blocksize - 1);
		size_t towrite = len;
		struct page *page;
		void *fsdata = NULL;
		char *kaddr;
		int err = 0;
		int tocopy;
		@@ -1938,7 +1939,7 @@ static ssize_t f2fs_quota_write(struct super_block *sb, int type,
		towrite);
		retry:
		err = a_ops->write_begin(NULL, mapping, off, tocopy, 0,
		&page, NULL);
		&page, &fsdata);
		if (unlikely(err)) {
		if (err == -ENOMEM) {
		congestion_wait(BLK_RW_ASYNC,
		@@ -1955,7 +1956,7 @@ retry:
		flush_dcache_page(page);

		a_ops->write_end(NULL, mapping, off, tocopy, tocopy,
		page, NULL);
		page, fsdata);
		offset = 0;
		towrite -= tocopy;
		off += tocopy;

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