Re: [PATCH v2] f2fs: fix to avoid NULL pointer dereference on se->discard_map

From: Vicente Bergas
Date: Tue Sep 04 2018 - 12:00:59 EST

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On Tue, Sep 4, 2018 at 5:45 PM, Chao Yu <chao@xxxxxxxxxx> wrote:
> On 2018/9/4 23:25, Vicente Bergas wrote:
>> On Mon, Sep 3, 2018 at 9:52 PM, Chao Yu <chao@xxxxxxxxxx> wrote:
>>> From: Chao Yu <yuchao0@xxxxxxxxxx>
>>>
>>> https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.kernel.org%2Fshow_bug.cgi%3Fid%3D200951&data=02%7C01%7C%7Cc2be7ee866b04268e69f08d6127aa973%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636716715374991374&sdata=E%2Boli5wWbe97f3QCdmAiIIZPEMInd9u221ldtVDqvtA%3D&reserved=0
>>>
>>> These is a NULL pointer dereference issue reported in bugzilla:
>>>
>>> Hi,
>>> in the setup there is a SATA SSD connected to a SATA-to-USB bridge.
>>>
>>> The disc is "Samsung SSD 850 PRO 256G" which supports TRIM.
>>> There are four partitions:
>>> sda1: FAT /boot
>>> sda2: F2FS /
>>> sda3: F2FS /home
>>> sda4: F2FS
>>>
>>> The bridge is ASMT1153e which uses the "uas" driver.
>>> There is no TRIM pass-through, so, when mounting it reports:
>>> mounting with "discard" option, but the device does not support discard
>>>
>>> The USB host is USB3.0 and UASP capable. It is the one on RK3399.
>>>
>>> Given this everything works fine, except there is no TRIM support.
>>>
>>> In order to enable TRIM a new UDEV rule is added [1]:
>>> /etc/udev/rules.d/10-sata-bridge-trim.rules:
>>> ACTION=="add|change", ATTRS{idVendor}=="174c", ATTRS{idProduct}=="55aa", SUBSYSTEM=="scsi_disk", ATTR{provisioning_mode}="unmap"
>>> After reboot any F2FS write hangs forever and dmesg reports:
>>> Unable to handle kernel NULL pointer dereference
>>>
>>> Also tested on a x86_64 system: works fine even with TRIM enabled.
>>> same disc
>>> same bridge
>>> different usb host controller
>>> different cpu architecture
>>> not root filesystem
>>>
>>> Regards,
>>> VicenÃ.
>>>
>>> [1] Post #5 in https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbbs.archlinux.org%2Fviewtopic.php%3Fid%3D236280&data=02%7C01%7C%7Cc2be7ee866b04268e69f08d6127aa973%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636716715374991374&sdata=tLP2J%2BL2MPDnqbLm1JcmJ7HfM%2F9j%2F0xc2MET2QSAjVE%3D&reserved=0
>>>
>>> Unable to handle kernel NULL pointer dereference at virtual address 000000000000003e
>>> Mem abort info:
>>> ESR = 0x96000004
>>> Exception class = DABT (current EL), IL = 32 bits
>>> SET = 0, FnV = 0
>>> EA = 0, S1PTW = 0
>>> Data abort info:
>>> ISV = 0, ISS = 0x00000004
>>> CM = 0, WnR = 0
>>> user pgtable: 4k pages, 48-bit VAs, pgdp = 00000000626e3122
>>> [000000000000003e] pgd=0000000000000000
>>> Internal error: Oops: 96000004 [#1] SMP
>>> Modules linked in: overlay snd_soc_hdmi_codec rc_cec dw_hdmi_i2s_audio dw_hdmi_cec snd_soc_simple_card snd_soc_simple_card_utils snd_soc_rockchip_i2s rockchip_rga snd_soc_rockchip_pcm rockchipdrm videobuf2_dma_sg v4l2_mem2mem rtc_rk808 videobuf2_memops analogix_dp videobuf2_v4l2 videobuf2_common dw_hdmi dw_wdt cec rc_core videodev drm_kms_helper media drm rockchip_thermal rockchip_saradc realtek drm_panel_orientation_quirks syscopyarea sysfillrect sysimgblt fb_sys_fops dwmac_rk stmmac_platform stmmac pwm_bl squashfs loop crypto_user gpio_keys hid_kensington
>>> CPU: 5 PID: 957 Comm: nvim Not tainted 4.19.0-rc1-1-ARCH #1
>>> Hardware name: Sapphire-RK3399 Board (DT)
>>> pstate: 00000005 (nzcv daif -PAN -UAO)
>>> pc : update_sit_entry+0x304/0x4b0
>>> lr : update_sit_entry+0x108/0x4b0
>>> sp : ffff00000ca13bd0
>>> x29: ffff00000ca13bd0 x28: 000000000000003e
>>> x27: 0000000000000020 x26: 0000000000080000
>>> x25: 0000000000000048 x24: ffff8000ebb85cf8
>>> x23: 0000000000000253 x22: 00000000ffffffff
>>> x21: 00000000000535f2 x20: 00000000ffffffdf
>>> x19: ffff8000eb9e6800 x18: ffff8000eb9e6be8
>>> x17: 0000000007ce6926 x16: 000000001c83ffa8
>>> x15: 0000000000000000 x14: ffff8000f602df90
>>> x13: 0000000000000006 x12: 0000000000000040
>>> x11: 0000000000000228 x10: 0000000000000000
>>> x9 : 0000000000000000 x8 : 0000000000000000
>>> x7 : 00000000000535f2 x6 : ffff8000ebff3440
>>> x5 : ffff8000ebff3440 x4 : ffff8000ebe3a6c8
>>> x3 : 00000000ffffffff x2 : 0000000000000020
>>> x1 : 0000000000000000 x0 : ffff8000eb9e5800
>>> Process nvim (pid: 957, stack limit = 0x0000000063a78320)
>>> Call trace:
>>> update_sit_entry+0x304/0x4b0
>>> f2fs_invalidate_blocks+0x98/0x140
>>> truncate_node+0x90/0x400
>>> f2fs_remove_inode_page+0xe8/0x340
>>> f2fs_evict_inode+0x2b0/0x408
>>> evict+0xe0/0x1e0
>>> iput+0x160/0x260
>>> do_unlinkat+0x214/0x298
>>> __arm64_sys_unlinkat+0x3c/0x68
>>> el0_svc_handler+0x94/0x118
>>> el0_svc+0x8/0xc
>>> Code: f9400800 b9488400 36080140 f9400f01 (387c4820)
>>> ---[ end trace a0f21a307118c477 ]---
>>>
>>> The reason is it is possible to enable discard flag on block queue via
>>> UDEV, but during mount, f2fs will initialize se->discard_map only if
>>> this flag is set, once the flag is set after mount, f2fs may dereference
>>> NULL pointer on se->discard_map.
>>>
>>> So this patch does below changes to fix this issue:
>>> - initialize and update se->discard_map all the time.
>>> - don't clear DISCARD option if device has no QUEUE_FLAG_DISCARD flag
>>> during mount.
>>> - don't issue small discard on zoned block device.
>>> - introduce some functions to enhance the readability.
>>>
>>> Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
>>> ---
>>> v2:
>>> - rebase to last dev branch.
>>> fs/f2fs/debug.c | 3 +--
>>> fs/f2fs/f2fs.h | 15 ++++++++---
>>> fs/f2fs/file.c | 2 +-
>>> fs/f2fs/segment.c | 65 ++++++++++++++++++++---------------------------
>>> fs/f2fs/super.c | 16 +++---------
>>> 5 files changed, 46 insertions(+), 55 deletions(-)
>>>
>>> diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
>>> index 214a968962a1..ebe649d9793c 100644
>>> --- a/fs/f2fs/debug.c
>>> +++ b/fs/f2fs/debug.c
>>> @@ -190,8 +190,7 @@ static void update_mem_info(struct f2fs_sb_info *sbi)
>>> si->base_mem += MAIN_SEGS(sbi) * sizeof(struct seg_entry);
>>> si->base_mem += f2fs_bitmap_size(MAIN_SEGS(sbi));
>>> si->base_mem += 2 * SIT_VBLOCK_MAP_SIZE * MAIN_SEGS(sbi);
>>> - if (f2fs_discard_en(sbi))
>>> - si->base_mem += SIT_VBLOCK_MAP_SIZE * MAIN_SEGS(sbi);
>>> + si->base_mem += SIT_VBLOCK_MAP_SIZE * MAIN_SEGS(sbi);
>>> si->base_mem += SIT_VBLOCK_MAP_SIZE;
>>> if (sbi->segs_per_sec > 1)
>>> si->base_mem += MAIN_SECS(sbi) * sizeof(struct sec_entry);
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index 96bde026636f..b575ec75ef87 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -3399,11 +3399,20 @@ static inline int get_blkz_type(struct f2fs_sb_info *sbi,
>>> }
>>> #endif
>>>
>>> -static inline bool f2fs_discard_en(struct f2fs_sb_info *sbi)
>>> +static inline bool f2fs_hw_should_discard(struct f2fs_sb_info *sbi)
>>> {
>>> - struct request_queue *q = bdev_get_queue(sbi->sb->s_bdev);
>>> + return f2fs_sb_has_blkzoned(sbi->sb);
>>> +}
>>>
>>> - return blk_queue_discard(q) || f2fs_sb_has_blkzoned(sbi->sb);
>>> +static inline bool f2fs_hw_support_discard(struct f2fs_sb_info *sbi)
>>> +{
>>> + return blk_queue_discard(bdev_get_queue(sbi->sb->s_bdev));
>>> +}
>>> +
>>> +static inline bool f2fs_realtime_discard_enable(struct f2fs_sb_info *sbi)
>>> +{
>>> + return (test_opt(sbi, DISCARD) && f2fs_hw_support_discard(sbi)) ||
>>> + f2fs_hw_should_discard(sbi);
>>> }
>>>
>>> static inline void set_opt_mode(struct f2fs_sb_info *sbi, unsigned int mt)
>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>> index 5474aaa274b9..ca66b3eb197a 100644
>>> --- a/fs/f2fs/file.c
>>> +++ b/fs/f2fs/file.c
>>> @@ -1978,7 +1978,7 @@ static int f2fs_ioc_fitrim(struct file *filp, unsigned long arg)
>>> if (!capable(CAP_SYS_ADMIN))
>>> return -EPERM;
>>>
>>> - if (!blk_queue_discard(q))
>>> + if (!f2fs_hw_support_discard(F2FS_SB(sb)))
>>> return -EOPNOTSUPP;
>>>
>>> if (copy_from_user(&range, (struct fstrim_range __user *)arg,
>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>> index 30779aaa9dba..c372ff755818 100644
>>> --- a/fs/f2fs/segment.c
>>> +++ b/fs/f2fs/segment.c
>>> @@ -1725,11 +1725,11 @@ static bool add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc,
>>> struct list_head *head = &SM_I(sbi)->dcc_info->entry_list;
>>> int i;
>>>
>>> - if (se->valid_blocks == max_blocks || !f2fs_discard_en(sbi))
>>> + if (se->valid_blocks == max_blocks || !f2fs_hw_support_discard(sbi))
>>> return false;
>>>
>>> if (!force) {
>>> - if (!test_opt(sbi, DISCARD) || !se->valid_blocks ||
>>> + if (!f2fs_realtime_discard_enable(sbi) || !se->valid_blocks ||
>>> SM_I(sbi)->dcc_info->nr_discards >=
>>> SM_I(sbi)->dcc_info->max_discards)
>>> return false;
>>> @@ -1835,7 +1835,7 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info *sbi,
>>> dirty_i->nr_dirty[PRE]--;
>>> }
>>>
>>> - if (!test_opt(sbi, DISCARD))
>>> + if (!f2fs_realtime_discard_enable(sbi))
>>> continue;
>>>
>>> if (force && start >= cpc->trim_start &&
>>> @@ -2025,8 +2025,7 @@ static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del)
>>> del = 0;
>>> }
>>>
>>> - if (f2fs_discard_en(sbi) &&
>>> - !f2fs_test_and_set_bit(offset, se->discard_map))
>>> + if (!f2fs_test_and_set_bit(offset, se->discard_map))
>>> sbi->discard_blks--;
>>>
>>> /* don't overwrite by SSR to keep node chain */
>>> @@ -2054,8 +2053,7 @@ static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del)
>>> del = 0;
>>> }
>>>
>>> - if (f2fs_discard_en(sbi) &&
>>> - f2fs_test_and_clear_bit(offset, se->discard_map))
>>> + if (f2fs_test_and_clear_bit(offset, se->discard_map))
>>> sbi->discard_blks++;
>>> }
>>> if (!f2fs_test_bit(offset, se->ckpt_valid_map))
>>> @@ -2671,7 +2669,7 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>>> * discard option. User configuration looks like using runtime discard
>>> * or periodic fstrim instead of it.
>>> */
>>> - if (test_opt(sbi, DISCARD))
>>> + if (f2fs_realtime_discard_enable(sbi))
>>> goto out;
>>>
>>> start_block = START_BLOCK(sbi, start_segno);
>>> @@ -3762,13 +3760,11 @@ static int build_sit_info(struct f2fs_sb_info *sbi)
>>> return -ENOMEM;
>>> #endif
>>>
>>> - if (f2fs_discard_en(sbi)) {
>>> - sit_i->sentries[start].discard_map
>>> - = f2fs_kzalloc(sbi, SIT_VBLOCK_MAP_SIZE,
>>> - GFP_KERNEL);
>>> - if (!sit_i->sentries[start].discard_map)
>>> - return -ENOMEM;
>>> - }
>>> + sit_i->sentries[start].discard_map
>>> + = f2fs_kzalloc(sbi, SIT_VBLOCK_MAP_SIZE,
>>> + GFP_KERNEL);
>>> + if (!sit_i->sentries[start].discard_map)
>>> + return -ENOMEM;
>>> }
>>>
>>> sit_i->tmp_map = f2fs_kzalloc(sbi, SIT_VBLOCK_MAP_SIZE, GFP_KERNEL);
>>> @@ -3916,18 +3912,16 @@ static int build_sit_entries(struct f2fs_sb_info *sbi)
>>> total_node_blocks += se->valid_blocks;
>>>
>>> /* build discard map only one time */
>>> - if (f2fs_discard_en(sbi)) {
>>> - if (is_set_ckpt_flags(sbi, CP_TRIMMED_FLAG)) {
>>> - memset(se->discard_map, 0xff,
>>> - SIT_VBLOCK_MAP_SIZE);
>>> - } else {
>>> - memcpy(se->discard_map,
>>> - se->cur_valid_map,
>>> - SIT_VBLOCK_MAP_SIZE);
>>> - sbi->discard_blks +=
>>> - sbi->blocks_per_seg -
>>> - se->valid_blocks;
>>> - }
>>> + if (is_set_ckpt_flags(sbi, CP_TRIMMED_FLAG)) {
>>> + memset(se->discard_map, 0xff,
>>> + SIT_VBLOCK_MAP_SIZE);
>>> + } else {
>>> + memcpy(se->discard_map,
>>> + se->cur_valid_map,
>>> + SIT_VBLOCK_MAP_SIZE);
>>> + sbi->discard_blks +=
>>> + sbi->blocks_per_seg -
>>> + se->valid_blocks;
>>> }
>>>
>>> if (sbi->segs_per_sec > 1)
>>> @@ -3965,16 +3959,13 @@ static int build_sit_entries(struct f2fs_sb_info *sbi)
>>> if (IS_NODESEG(se->type))
>>> total_node_blocks += se->valid_blocks;
>>>
>>> - if (f2fs_discard_en(sbi)) {
>>> - if (is_set_ckpt_flags(sbi, CP_TRIMMED_FLAG)) {
>>> - memset(se->discard_map, 0xff,
>>> - SIT_VBLOCK_MAP_SIZE);
>>> - } else {
>>> - memcpy(se->discard_map, se->cur_valid_map,
>>> - SIT_VBLOCK_MAP_SIZE);
>>> - sbi->discard_blks += old_valid_blocks;
>>> - sbi->discard_blks -= se->valid_blocks;
>>> - }
>>> + if (is_set_ckpt_flags(sbi, CP_TRIMMED_FLAG)) {
>>> + memset(se->discard_map, 0xff, SIT_VBLOCK_MAP_SIZE);
>>> + } else {
>>> + memcpy(se->discard_map, se->cur_valid_map,
>>> + SIT_VBLOCK_MAP_SIZE);
>>> + sbi->discard_blks += old_valid_blocks;
>>> + sbi->discard_blks -= se->valid_blocks;
>>> }
>>>
>>> if (sbi->segs_per_sec > 1) {
>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>> index 53d70b64fea1..5cad0f7687e9 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -360,7 +360,6 @@ static int f2fs_check_quota_options(struct f2fs_sb_info *sbi)
>>> static int parse_options(struct super_block *sb, char *options)
>>> {
>>> struct f2fs_sb_info *sbi = F2FS_SB(sb);
>>> - struct request_queue *q;
>>> substring_t args[MAX_OPT_ARGS];
>>> char *p, *name;
>>> int arg = 0;
>>> @@ -415,14 +414,7 @@ static int parse_options(struct super_block *sb, char *options)
>>> return -EINVAL;
>>> break;
>>> case Opt_discard:
>>> - q = bdev_get_queue(sb->s_bdev);
>>> - if (blk_queue_discard(q)) {
>>> - set_opt(sbi, DISCARD);
>>> - } else if (!f2fs_sb_has_blkzoned(sb)) {
>>> - f2fs_msg(sb, KERN_WARNING,
>>> - "mounting with \"discard\" option, but "
>>> - "the device does not support discard");
>>> - }
>>> + set_opt(sbi, DISCARD);
>>> break;
>>> case Opt_nodiscard:
>>> if (f2fs_sb_has_blkzoned(sb)) {
>>> @@ -1032,7 +1024,8 @@ static void f2fs_put_super(struct super_block *sb)
>>> /* be sure to wait for any on-going discard commands */
>>> dropped = f2fs_wait_discard_bios(sbi);
>>>
>>> - if (f2fs_discard_en(sbi) && !sbi->discard_blks && !dropped) {
>>> + if ((f2fs_hw_support_discard(sbi) || f2fs_hw_should_discard(sbi)) &&
>>> + !sbi->discard_blks && !dropped) {
>>> struct cp_control cpc = {
>>> .reason = CP_UMOUNT | CP_TRIMMED,
>>> };
>>> @@ -1399,8 +1392,7 @@ static void default_options(struct f2fs_sb_info *sbi)
>>> set_opt(sbi, NOHEAP);
>>> sbi->sb->s_flags |= SB_LAZYTIME;
>>> set_opt(sbi, FLUSH_MERGE);
>>> - if (blk_queue_discard(bdev_get_queue(sbi->sb->s_bdev)))
>>> - set_opt(sbi, DISCARD);
>>> + set_opt(sbi, DISCARD);
>>> if (f2fs_sb_has_blkzoned(sbi->sb))
>>> set_opt_mode(sbi, F2FS_MOUNT_LFS);
>>> else
>>> --
>>> 2.18.0
>>>
>>
>> Hi,
>> just tested and it works fine: no more segfaults.
>> How can i check that TRIM is indeed being used?
>
> You can check discard trace:
>
> echo 1 > /sys/kernel/debug/tracing/events/f2fs/f2fs_issue_discard/enable
> cat /sys/kernel/debug/tracing/trace_pipe

I confirm that there are discarded blocks in two filesystems:
a.- The root filesystem, which had the discard option applied after mount.
b.- A non-root filesystem, which had the discard option applied before mount.
So, complete success!

Regards,
VicenÃ.

>
> Thanks,
>
>>
>> Tested-by: Vicente Bergas <vicencb@xxxxxxxxx>
>>
>> Regards,
>> VicenÃ.
>>

Next message: Takashi Iwai: "[PATCH 08/29] staging: bcm2835-audio: Drop useless running flag and check"
Previous message: Takashi Iwai: "[PATCH 11/29] staging: bcm2835-audio: Use PCM runtime values instead"
In reply to: Chao Yu: "Re: [PATCH v2] f2fs: fix to avoid NULL pointer dereference on se->discard_map"
Next in thread: Chao Yu: "Re: [PATCH v2] f2fs: fix to avoid NULL pointer dereference on se->discard_map"
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