From: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
To: tytso@mit.edu, adilger.kernel@dilger.ca
Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
syzbot+a8b4b0c60155e87e9484@syzkaller.appspotmail.com
Subject: [PATCH] fs/ext4: fix integer overflow in s_log_groups_per_flex
Date: Wed, 3 Feb 2021 19:43:51 +0600 [thread overview]
Message-ID: <20210203134351.1697508-1-snovitoll@gmail.com> (raw)
syzbot found UBSAN: shift-out-of-bounds in ext4_mb_init [1], when
1 << sbi->s_es->s_log_groups_per_flex is bigger than UINT_MAX,
where sbi->s_mb_prefetch is unsigned integer type.
32 is the maximum allowed power of s_log_groups_per_flex. Following if
check will also trigger UBSAN shift-out-of-bound:
if (1 << sbi->s_es->s_log_groups_per_flex > UINT_MAX) {
So I'm checking it against the raw number, perhaps there is another way
to calculate UINT_MAX max power. Also use min_t as to make sure it's
uint type.
[1] UBSAN: shift-out-of-bounds in fs/ext4/mballoc.c:2713:24
shift exponent 60 is too large for 32-bit type 'int'
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x137/0x1be lib/dump_stack.c:120
ubsan_epilogue lib/ubsan.c:148 [inline]
__ubsan_handle_shift_out_of_bounds+0x432/0x4d0 lib/ubsan.c:395
ext4_mb_init_backend fs/ext4/mballoc.c:2713 [inline]
ext4_mb_init+0x19bc/0x19f0 fs/ext4/mballoc.c:2898
ext4_fill_super+0xc2ec/0xfbe0 fs/ext4/super.c:4983
Reported-by: syzbot+a8b4b0c60155e87e9484@syzkaller.appspotmail.com
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
---
fs/ext4/mballoc.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 99bf091fee10..e1e7ffbba1a6 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2709,8 +2709,15 @@ static int ext4_mb_init_backend(struct super_block *sb)
}
if (ext4_has_feature_flex_bg(sb)) {
- /* a single flex group is supposed to be read by a single IO */
- sbi->s_mb_prefetch = min(1 << sbi->s_es->s_log_groups_per_flex,
+ /* a single flex group is supposed to be read by a single IO.
+ * 2 ^ s_log_groups_per_flex != UINT_MAX as s_mb_prefetch is
+ * unsigned integer, so the maximum shift is 32.
+ */
+ if (sbi->s_es->s_log_groups_per_flex > 32) {
+ ext4_msg(sb, KERN_ERR, "too many log groups per flexible block group");
+ goto err_freesgi;
+ }
+ sbi->s_mb_prefetch = min_t(uint, 1 << sbi->s_es->s_log_groups_per_flex,
BLK_MAX_SEGMENT_SIZE >> (sb->s_blocksize_bits - 9));
sbi->s_mb_prefetch *= 8; /* 8 prefetch IOs in flight at most */
} else {
--
2.25.1
next reply other threads:[~2021-02-03 13:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-03 13:43 Sabyrzhan Tasbolatov [this message]
2021-02-23 17:01 ` [PATCH] fs/ext4: fix integer overflow in s_log_groups_per_flex Jan Kara
2021-02-24 9:58 ` [PATCH v2] " Sabyrzhan Tasbolatov
2021-02-24 10:05 ` Jan Kara
2021-03-05 14:32 ` Theodore Ts'o
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