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SubjectRe: [PATCH v2] f2fs: fix to avoid NULL pointer dereference on se->discard_map
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On 2018/9/4 23:25, Vicente Bergas wrote:
> On Mon, Sep 3, 2018 at 9:52 PM, Chao Yu <chao@kernel.org> wrote:
>> From: Chao Yu <yuchao0@huawei.com>
>>
>> https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.kernel.org%2Fshow_bug.cgi%3Fid%3D200951&amp;data=02%7C01%7C%7Cc2be7ee866b04268e69f08d6127aa973%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636716715374991374&amp;sdata=E%2Boli5wWbe97f3QCdmAiIIZPEMInd9u221ldtVDqvtA%3D&amp;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,
>> Vicenç.
>>
>> [1] Post #5 in https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbbs.archlinux.org%2Fviewtopic.php%3Fid%3D236280&amp;data=02%7C01%7C%7Cc2be7ee866b04268e69f08d6127aa973%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636716715374991374&amp;sdata=tLP2J%2BL2MPDnqbLm1JcmJ7HfM%2F9j%2F0xc2MET2QSAjVE%3D&amp;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@huawei.com>
>> ---
>> 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

Thanks,

>
> Tested-by: Vicente Bergas <vicencb@gmail.com>
>
> Regards,
> Vicenç.
>

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