linux-kernel - [PATCH] jffs2: check that raw node were preallocated before writing summary

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Message-ID: <20250307163409.13491-2-a.sadovnikov@ispras.ru>
Date: Fri,  7 Mar 2025 16:34:09 +0000
From: Artem Sadovnikov <a.sadovnikov@...ras.ru>
To: linux-mtd@...ts.infradead.org
Cc: Artem Sadovnikov <a.sadovnikov@...ras.ru>,
	David Woodhouse <dwmw2@...radead.org>,
	Richard Weinberger <richard@....at>,
	linux-kernel@...r.kernel.org,
	lvc-project@...uxtesting.org,
	stable@...r.kernel.org
Subject: [PATCH] jffs2: check that raw node were preallocated before writing summary

Syzkaller detected a kernel bug in jffs2_link_node_ref, caused by fault
injection in jffs2_prealloc_raw_node_refs. jffs2_sum_write_sumnode doesn't
check return value of jffs2_prealloc_raw_node_refs and simply lets any
error propagate into jffs2_sum_write_data, which eventually calls
jffs2_link_node_ref in order to link the summary to an expectedly allocated
node.

kernel BUG at fs/jffs2/nodelist.c:592!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
CPU: 1 PID: 31277 Comm: syz-executor.7 Not tainted 6.1.128-syzkaller-00139-ge10f83ca10a1 #0
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
RIP: 0010:jffs2_link_node_ref+0x570/0x690 fs/jffs2/nodelist.c:592
Call Trace:
 <TASK>
 jffs2_sum_write_data fs/jffs2/summary.c:841 [inline]
 jffs2_sum_write_sumnode+0xd1a/0x1da0 fs/jffs2/summary.c:874
 jffs2_do_reserve_space+0xa18/0xd60 fs/jffs2/nodemgmt.c:388
 jffs2_reserve_space+0x55f/0xaa0 fs/jffs2/nodemgmt.c:197
 jffs2_write_inode_range+0x246/0xb50 fs/jffs2/write.c:362
 jffs2_write_end+0x726/0x15d0 fs/jffs2/file.c:301
 generic_perform_write+0x314/0x5d0 mm/filemap.c:3856
 __generic_file_write_iter+0x2ae/0x4d0 mm/filemap.c:3973
 generic_file_write_iter+0xe3/0x350 mm/filemap.c:4005
 call_write_iter include/linux/fs.h:2265 [inline]
 do_iter_readv_writev+0x20f/0x3c0 fs/read_write.c:735
 do_iter_write+0x186/0x710 fs/read_write.c:861
 vfs_iter_write+0x70/0xa0 fs/read_write.c:902
 iter_file_splice_write+0x73b/0xc90 fs/splice.c:685
 do_splice_from fs/splice.c:763 [inline]
 direct_splice_actor+0x10c/0x170 fs/splice.c:950
 splice_direct_to_actor+0x337/0xa10 fs/splice.c:896
 do_splice_direct+0x1a9/0x280 fs/splice.c:1002
 do_sendfile+0xb13/0x12c0 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x1cf/0x210 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

Fix this issue by checking return value of jffs2_prealloc_raw_node_refs
before calling jffs2_sum_write_data.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Cc: stable@...r.kernel.org
Fixes: 2f785402f39b ("[JFFS2] Reduce visibility of raw_node_ref to upper layers of JFFS2 code.")
Signed-off-by: Artem Sadovnikov <a.sadovnikov@...ras.ru>
---
 fs/jffs2/summary.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/jffs2/summary.c b/fs/jffs2/summary.c
index 4fe64519870f1..d83372d3e1a07 100644
--- a/fs/jffs2/summary.c
+++ b/fs/jffs2/summary.c
@@ -858,7 +858,10 @@ int jffs2_sum_write_sumnode(struct jffs2_sb_info *c)
 	spin_unlock(&c->erase_completion_lock);

 	jeb = c->nextblock;
-	jffs2_prealloc_raw_node_refs(c, jeb, 1);
+	ret = jffs2_prealloc_raw_node_refs(c, jeb, 1);
+
+	if (ret)
+		goto out;

 	if (!c->summary->sum_num || !c->summary->sum_list_head) {
 		JFFS2_WARNING("Empty summary info!!!\n");
@@ -872,6 +875,8 @@ int jffs2_sum_write_sumnode(struct jffs2_sb_info *c)
 	datasize += padsize;

 	ret = jffs2_sum_write_data(c, jeb, infosize, datasize, padsize);
+
+out:
 	spin_lock(&c->erase_completion_lock);
 	return ret;
 }
-- 
2.43.0