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Subject[PATCH 4.19 112/115] ubifs: ubifs_tnc_start_commit: Fix OOB in layout_in_gaps
Date
From: Zhihao Cheng <chengzhihao1@huawei.com>

[ Upstream commit 6abf57262166b4f4294667fb5206ae7ba1ba96f5 ]

Running stress-test test_2 in mtd-utils on ubi device, sometimes we can
get following oops message:

BUG: unable to handle page fault for address: ffffffff00000140
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 280a067 P4D 280a067 PUD 0
Oops: 0000 [#1] SMP
CPU: 0 PID: 60 Comm: kworker/u16:1 Kdump: loaded Not tainted 5.2.0 #13
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0
-0-ga698c8995f-prebuilt.qemu.org 04/01/2014
Workqueue: writeback wb_workfn (flush-ubifs_0_0)
RIP: 0010:rb_next_postorder+0x2e/0xb0
Code: 80 db 03 01 48 85 ff 0f 84 97 00 00 00 48 8b 17 48 83 05 bc 80 db
03 01 48 83 e2 fc 0f 84 82 00 00 00 48 83 05 b2 80 db 03 01 <48> 3b 7a
10 48 89 d0 74 02 f3 c3 48 8b 52 08 48 83 05 a3 80 db 03
RSP: 0018:ffffc90000887758 EFLAGS: 00010202
RAX: ffff888129ae4700 RBX: ffff888138b08400 RCX: 0000000080800001
RDX: ffffffff00000130 RSI: 0000000080800024 RDI: ffff888138b08400
RBP: ffff888138b08400 R08: ffffea0004a6b920 R09: 0000000000000000
R10: ffffc90000887740 R11: 0000000000000001 R12: ffff888128d48000
R13: 0000000000000800 R14: 000000000000011e R15: 00000000000007c8
FS: 0000000000000000(0000) GS:ffff88813ba00000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffff00000140 CR3: 000000013789d000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
destroy_old_idx+0x5d/0xa0 [ubifs]
ubifs_tnc_start_commit+0x4fe/0x1380 [ubifs]
do_commit+0x3eb/0x830 [ubifs]
ubifs_run_commit+0xdc/0x1c0 [ubifs]

Above Oops are due to the slab-out-of-bounds happened in do-while of
function layout_in_gaps indirectly called by ubifs_tnc_start_commit. In
function layout_in_gaps, there is a do-while loop placing index nodes
into the gaps created by obsolete index nodes in non-empty index LEBs
until rest index nodes can totally be placed into pre-allocated empty
LEBs. @c->gap_lebs points to a memory area(integer array) which records
LEB numbers used by 'in-the-gaps' method. Whenever a fitable index LEB
is found, corresponding lnum will be incrementally written into the
memory area pointed by @c->gap_lebs. The size
((@c->lst.idx_lebs + 1) * sizeof(int)) of memory area is allocated before
do-while loop and can not be changed in the loop. But @c->lst.idx_lebs
could be increased by function ubifs_change_lp (called by
layout_leb_in_gaps->ubifs_find_dirty_idx_leb->get_idx_gc_leb) during the
loop. So, sometimes oob happens when number of cycles in do-while loop
exceeds the original value of @c->lst.idx_lebs. See detail in
https://bugzilla.kernel.org/show_bug.cgi?id=204229.
This patch fixes oob in layout_in_gaps.

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ubifs/tnc_commit.c | 34 +++++++++++++++++++++++++++-------
1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/fs/ubifs/tnc_commit.c b/fs/ubifs/tnc_commit.c
index dba87d09b989..95630f9f40dd 100644
--- a/fs/ubifs/tnc_commit.c
+++ b/fs/ubifs/tnc_commit.c
@@ -219,7 +219,7 @@ static int is_idx_node_in_use(struct ubifs_info *c, union ubifs_key *key,
/**
* layout_leb_in_gaps - layout index nodes using in-the-gaps method.
* @c: UBIFS file-system description object
- * @p: return LEB number here
+ * @p: return LEB number in @c->gap_lebs[p]
*
* This function lays out new index nodes for dirty znodes using in-the-gaps
* method of TNC commit.
@@ -228,7 +228,7 @@ static int is_idx_node_in_use(struct ubifs_info *c, union ubifs_key *key,
* This function returns the number of index nodes written into the gaps, or a
* negative error code on failure.
*/
-static int layout_leb_in_gaps(struct ubifs_info *c, int *p)
+static int layout_leb_in_gaps(struct ubifs_info *c, int p)
{
struct ubifs_scan_leb *sleb;
struct ubifs_scan_node *snod;
@@ -243,7 +243,7 @@ static int layout_leb_in_gaps(struct ubifs_info *c, int *p)
* filled, however we do not check there at present.
*/
return lnum; /* Error code */
- *p = lnum;
+ c->gap_lebs[p] = lnum;
dbg_gc("LEB %d", lnum);
/*
* Scan the index LEB. We use the generic scan for this even though
@@ -362,7 +362,7 @@ static int get_leb_cnt(struct ubifs_info *c, int cnt)
*/
static int layout_in_gaps(struct ubifs_info *c, int cnt)
{
- int err, leb_needed_cnt, written, *p;
+ int err, leb_needed_cnt, written, p = 0, old_idx_lebs, *gap_lebs;

dbg_gc("%d znodes to write", cnt);

@@ -371,9 +371,9 @@ static int layout_in_gaps(struct ubifs_info *c, int cnt)
if (!c->gap_lebs)
return -ENOMEM;

- p = c->gap_lebs;
+ old_idx_lebs = c->lst.idx_lebs;
do {
- ubifs_assert(c, p < c->gap_lebs + c->lst.idx_lebs);
+ ubifs_assert(c, p < c->lst.idx_lebs);
written = layout_leb_in_gaps(c, p);
if (written < 0) {
err = written;
@@ -399,9 +399,29 @@ static int layout_in_gaps(struct ubifs_info *c, int cnt)
leb_needed_cnt = get_leb_cnt(c, cnt);
dbg_gc("%d znodes remaining, need %d LEBs, have %d", cnt,
leb_needed_cnt, c->ileb_cnt);
+ /*
+ * Dynamically change the size of @c->gap_lebs to prevent
+ * oob, because @c->lst.idx_lebs could be increased by
+ * function @get_idx_gc_leb (called by layout_leb_in_gaps->
+ * ubifs_find_dirty_idx_leb) during loop. Only enlarge
+ * @c->gap_lebs when needed.
+ *
+ */
+ if (leb_needed_cnt > c->ileb_cnt && p >= old_idx_lebs &&
+ old_idx_lebs < c->lst.idx_lebs) {
+ old_idx_lebs = c->lst.idx_lebs;
+ gap_lebs = krealloc(c->gap_lebs, sizeof(int) *
+ (old_idx_lebs + 1), GFP_NOFS);
+ if (!gap_lebs) {
+ kfree(c->gap_lebs);
+ c->gap_lebs = NULL;
+ return -ENOMEM;
+ }
+ c->gap_lebs = gap_lebs;
+ }
} while (leb_needed_cnt > c->ileb_cnt);

- *p = -1;
+ c->gap_lebs[p] = -1;
return 0;
}

--
2.20.1


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