On 2024/2/14 0:58, Jan Kara wrote:
On Fri 26-01-24 16:57:13, Baokun Li wrote:
We can easily trigger a BUG_ON by using the following commands:
mount /dev/$disk /tmp/test echo 2147483650 > /sys/fs/ext4/$disk/mb_group_prealloc echo test > /tmp/test/file && sync================================================================== kernel BUG at fs/ext4/mballoc.c:2029! invalid opcode: 0000 [#1] PREEMPT SMP PTI CPU: 3 PID: 320 Comm: kworker/u36:1 Not tainted 6.8.0-rc1 #462 RIP: 0010:mb_mark_used+0x358/0x370 [...] Call Trace: ext4_mb_use_best_found+0x56/0x140 ext4_mb_complex_scan_group+0x196/0x2f0 ext4_mb_regular_allocator+0xa92/0xf00 ext4_mb_new_blocks+0x302/0xbc0 ext4_ext_map_blocks+0x95a/0xef0 ext4_map_blocks+0x2b1/0x680 ext4_do_writepages+0x733/0xbd0 [...] ==================================================================
In ext4_mb_normalize_group_request(): ac->ac_g_ex.fe_len = EXT4_SB(sb)->s_mb_group_prealloc;
Here fe_len is of type int, but s_mb_group_prealloc is of type unsigned int, so setting s_mb_group_prealloc to 2147483650 overflows fe_len to a negative number, which ultimately triggers a BUG_ON() in mb_mark_used().
Therefore, we add attr_pointer_pi (aka positive int attr pointer) with a value range of 0-INT_MAX to avoid the above problem. In addition to the mb_group_prealloc sysfs interface, the following interfaces also have uint to int conversions that result in overflows, and are also fixed.
err_ratelimit_burst msg_ratelimit_burst warning_ratelimit_burst err_ratelimit_interval_ms msg_ratelimit_interval_ms warning_ratelimit_interval_ms mb_best_avail_max_trim_order
CC: stable@vger.kernel.org Signed-off-by: Baokun Li libaokun1@huawei.com
I don't think you need to change s_mb_group_prealloc here and then restrict it even further in the next patch. I'd just leave it alone here.
Yes, we could put the next patch before this one, but using s_mb_group_prealloc as an example makes it easier to understand why the attr_pointer_pi case is added here.There are several other variables that don't have more convincing examples.
Also I think that limiting mb_best_avail_max_trim_order to 64 instead of INT_MAX will make us more resilient to surprises in the future :) But I don't really insist.
Honza
I think it's enough here to make sure that mb_best_avail_max_trim_order is a positive number, since we always make sure that min_order is not less than 0, as follows:
order = fls(ac->ac_g_ex.fe_len) - 1; min_order = order - sbi->s_mb_best_avail_max_trim_order; if (min_order < 0) min_order = 0;
An oversized mb_best_avail_max_trim_order can be interpreted as always being CR_ANY_FREE. 😄
fs/ext4/sysfs.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-)
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c index a5d657fa05cb..6f9f96e00f2f 100644 --- a/fs/ext4/sysfs.c +++ b/fs/ext4/sysfs.c @@ -30,6 +30,7 @@ typedef enum { attr_first_error_time, attr_last_error_time, attr_feature,
- attr_pointer_pi, attr_pointer_ui, attr_pointer_ul, attr_pointer_u64,
@@ -178,6 +179,9 @@ static struct ext4_attr ext4_attr_##_name = { \ #define EXT4_RO_ATTR_ES_STRING(_name,_elname,_size) \ EXT4_ATTR_STRING(_name, 0444, _size, ext4_super_block, _elname) +#define EXT4_RW_ATTR_SBI_PI(_name,_elname) \
- EXT4_ATTR_OFFSET(_name, 0644, pointer_pi, ext4_sb_info, _elname)
- #define EXT4_RW_ATTR_SBI_UI(_name,_elname) \ EXT4_ATTR_OFFSET(_name, 0644, pointer_ui, ext4_sb_info, _elname)
@@ -213,17 +217,17 @@ EXT4_RW_ATTR_SBI_UI(mb_max_to_scan, s_mb_max_to_scan); EXT4_RW_ATTR_SBI_UI(mb_min_to_scan, s_mb_min_to_scan); EXT4_RW_ATTR_SBI_UI(mb_order2_req, s_mb_order2_reqs); EXT4_RW_ATTR_SBI_UI(mb_stream_req, s_mb_stream_request); -EXT4_RW_ATTR_SBI_UI(mb_group_prealloc, s_mb_group_prealloc); +EXT4_RW_ATTR_SBI_PI(mb_group_prealloc, s_mb_group_prealloc); EXT4_RW_ATTR_SBI_UI(mb_max_linear_groups, s_mb_max_linear_groups); EXT4_RW_ATTR_SBI_UI(extent_max_zeroout_kb, s_extent_max_zeroout_kb); EXT4_ATTR(trigger_fs_error, 0200, trigger_test_error); -EXT4_RW_ATTR_SBI_UI(err_ratelimit_interval_ms, s_err_ratelimit_state.interval); -EXT4_RW_ATTR_SBI_UI(err_ratelimit_burst, s_err_ratelimit_state.burst); -EXT4_RW_ATTR_SBI_UI(warning_ratelimit_interval_ms, s_warning_ratelimit_state.interval); -EXT4_RW_ATTR_SBI_UI(warning_ratelimit_burst, s_warning_ratelimit_state.burst); -EXT4_RW_ATTR_SBI_UI(msg_ratelimit_interval_ms, s_msg_ratelimit_state.interval); -EXT4_RW_ATTR_SBI_UI(msg_ratelimit_burst, s_msg_ratelimit_state.burst); -EXT4_RW_ATTR_SBI_UI(mb_best_avail_max_trim_order, s_mb_best_avail_max_trim_order); +EXT4_RW_ATTR_SBI_PI(err_ratelimit_interval_ms, s_err_ratelimit_state.interval); +EXT4_RW_ATTR_SBI_PI(err_ratelimit_burst, s_err_ratelimit_state.burst); +EXT4_RW_ATTR_SBI_PI(warning_ratelimit_interval_ms, s_warning_ratelimit_state.interval); +EXT4_RW_ATTR_SBI_PI(warning_ratelimit_burst, s_warning_ratelimit_state.burst); +EXT4_RW_ATTR_SBI_PI(msg_ratelimit_interval_ms, s_msg_ratelimit_state.interval); +EXT4_RW_ATTR_SBI_PI(msg_ratelimit_burst, s_msg_ratelimit_state.burst); +EXT4_RW_ATTR_SBI_PI(mb_best_avail_max_trim_order, s_mb_best_avail_max_trim_order); #ifdef CONFIG_EXT4_DEBUG EXT4_RW_ATTR_SBI_UL(simulate_fail, s_simulate_fail); #endif @@ -376,6 +380,7 @@ static ssize_t ext4_generic_attr_show(struct ext4_attr *a, switch (a->attr_id) { case attr_inode_readahead:
- case attr_pointer_pi: case attr_pointer_ui: if (a->attr_ptr == ptr_ext4_super_block_offset) return sysfs_emit(buf, "%u\n", le32_to_cpup(ptr));
@@ -448,6 +453,10 @@ static ssize_t ext4_generic_attr_store(struct ext4_attr *a, return ret; switch (a->attr_id) {
- case attr_pointer_pi:
if ((int)t < 0)return -EINVAL;fallthrough;-- 2.31.1
Thanks!