From: Takashi Iwai tiwai@suse.de
mainline inclusion from mainline-v5.7-rc1 commit 17bb60b74124e9491d593e2601e3afe14daa2f57 category: bugfix bugzilla: 33322 CVE: NA
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Since snprintf() returns the would-be-output size instead of the actual output size, the succeeding calls may go beyond the given buffer limit. Fix it by replacing with scnprintf().
Signed-off-by: Takashi Iwai tiwai@suse.de Reviewed-by: Darrick J. Wong darrick.wong@oracle.com Signed-off-by: Darrick J. Wong darrick.wong@oracle.com Signed-off-by: yu kuai yukuai3@huawei.com Reviewed-by: zhangyi (F) yi.zhang@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/xfs/xfs_stats.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/fs/xfs/xfs_stats.c b/fs/xfs/xfs_stats.c index 740ac9674848..0373d9ea7334 100644 --- a/fs/xfs/xfs_stats.c +++ b/fs/xfs/xfs_stats.c @@ -58,13 +58,13 @@ int xfs_stats_format(struct xfsstats __percpu *stats, char *buf) /* Loop over all stats groups */
for (i = j = 0; i < ARRAY_SIZE(xstats); i++) { - len += snprintf(buf + len, PATH_MAX - len, "%s", + len += scnprintf(buf + len, PATH_MAX - len, "%s", xstats[i].desc); /* inner loop does each group */ for (; j < xstats[i].endpoint; j++) - len += snprintf(buf + len, PATH_MAX - len, " %u", + len += scnprintf(buf + len, PATH_MAX - len, " %u", counter_val(stats, j)); - len += snprintf(buf + len, PATH_MAX - len, "\n"); + len += scnprintf(buf + len, PATH_MAX - len, "\n"); } /* extra precision counters */ for_each_possible_cpu(i) { @@ -73,9 +73,9 @@ int xfs_stats_format(struct xfsstats __percpu *stats, char *buf) xs_read_bytes += per_cpu_ptr(stats, i)->s.xs_read_bytes; }
- len += snprintf(buf + len, PATH_MAX-len, "xpc %Lu %Lu %Lu\n", + len += scnprintf(buf + len, PATH_MAX-len, "xpc %Lu %Lu %Lu\n", xs_xstrat_bytes, xs_write_bytes, xs_read_bytes); - len += snprintf(buf + len, PATH_MAX-len, "debug %u\n", + len += scnprintf(buf + len, PATH_MAX-len, "debug %u\n", #if defined(DEBUG) 1); #else
From: "Darrick J. Wong" darrick.wong@oracle.com
mainline inclusion from mainline-v5.7-rc1 commit 27fb5a72f50aa770dd38b0478c07acacef97e3e7 category: bugfix bugzilla: 33320 CVE: NA
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I noticed that fsfreeze can take a very long time to freeze an XFS if there happens to be a GETFSMAP caller running in the background. I also happened to notice the following in dmesg:
------------[ cut here ]------------ WARNING: CPU: 2 PID: 43492 at fs/xfs/xfs_super.c:853 xfs_quiesce_attr+0x83/0x90 [xfs] Modules linked in: xfs libcrc32c ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 ip_set_hash_ip ip_set_hash_net xt_tcpudp xt_set ip_set_hash_mac ip_set nfnetlink ip6table_filter ip6_tables bfq iptable_filter sch_fq_codel ip_tables x_tables nfsv4 af_packet [last unloaded: xfs] CPU: 2 PID: 43492 Comm: xfs_io Not tainted 5.6.0-rc4-djw #rc4 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-1ubuntu1 04/01/2014 RIP: 0010:xfs_quiesce_attr+0x83/0x90 [xfs] Code: 7c 07 00 00 85 c0 75 22 48 89 df 5b e9 96 c1 00 00 48 c7 c6 b0 2d 38 a0 48 89 df e8 57 64 ff ff 8b 83 7c 07 00 00 85 c0 74 de <0f> 0b 48 89 df 5b e9 72 c1 00 00 66 90 0f 1f 44 00 00 41 55 41 54 RSP: 0018:ffffc900030f3e28 EFLAGS: 00010202 RAX: 0000000000000001 RBX: ffff88802ac54000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff81e4a6f0 RDI: 00000000ffffffff RBP: ffff88807859f070 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000010 R12: 0000000000000000 R13: ffff88807859f388 R14: ffff88807859f4b8 R15: ffff88807859f5e8 FS: 00007fad1c6c0fc0(0000) GS:ffff88807e000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f0c7d237000 CR3: 0000000077f01003 CR4: 00000000001606a0 Call Trace: xfs_fs_freeze+0x25/0x40 [xfs] freeze_super+0xc8/0x180 do_vfs_ioctl+0x70b/0x750 ? __fget_files+0x135/0x210 ksys_ioctl+0x3a/0xb0 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x50/0x1a0 entry_SYSCALL_64_after_hwframe+0x49/0xbe
These two things appear to be related. The assertion trips when another thread initiates a fsmap request (which uses an empty transaction) after the freezer waited for m_active_trans to hit zero but before the the freezer executes the WARN_ON just prior to calling xfs_log_quiesce.
The lengthy delays in freezing happen because the freezer calls xfs_wait_buftarg to clean out the buffer lru list. Meanwhile, the GETFSMAP caller is continuing to grab and release buffers, which means that it can take a very long time for the buffer lru list to empty out.
We fix both of these races by calling sb_start_write to obtain freeze protection while using empty transactions for GETFSMAP and for metadata scrubbing. The other two users occur during mount, during which time we cannot fs freeze.
Signed-off-by: Darrick J. Wong darrick.wong@oracle.com Reviewed-by: Dave Chinner dchinner@redhat.com
Conflict: fs/xfs/scrub/scrub.c Signed-off-by: yu kuai yukuai3@huawei.com Reviewed-by: zhangyi (F) yi.zhang@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/xfs/scrub/scrub.c | 10 ++++++++++ fs/xfs/xfs_fsmap.c | 9 +++++++++ fs/xfs/xfs_trans.c | 5 +++++ 3 files changed, 24 insertions(+)
diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c index 4bfae1e61d30..97ecb627c4e4 100644 --- a/fs/xfs/scrub/scrub.c +++ b/fs/xfs/scrub/scrub.c @@ -186,6 +186,7 @@ xchk_teardown( xfs_irele(sc->ip); sc->ip = NULL; } + sb_end_write(sc->mp->m_super); if (sc->has_quotaofflock) mutex_unlock(&sc->mp->m_quotainfo->qi_quotaofflock); if (sc->buf) { @@ -512,6 +513,15 @@ xfs_scrub_metadata( sc.ops = &meta_scrub_ops[sm->sm_type]; sc.try_harder = try_harder; sc.sa.agno = NULLAGNUMBER; + + /* + * If freeze runs concurrently with a scrub, the freeze can be delayed + * indefinitely as we walk the filesystem and iterate over metadata + * buffers. Freeze quiesces the log (which waits for the buffer LRU to + * be emptied) and that won't happen while checking is running. + */ + sb_start_write(mp->m_super); + error = sc.ops->setup(&sc, ip); if (error) goto out_teardown; diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c index 3d76a9e35870..910f0e9b5c68 100644 --- a/fs/xfs/xfs_fsmap.c +++ b/fs/xfs/xfs_fsmap.c @@ -899,6 +899,14 @@ xfs_getfsmap( info.format_arg = arg; info.head = head;
+ /* + * If fsmap runs concurrently with a scrub, the freeze can be delayed + * indefinitely as we walk the rmapbt and iterate over metadata + * buffers. Freeze quiesces the log (which waits for the buffer LRU to + * be emptied) and that won't happen while we're reading buffers. + */ + sb_start_write(mp->m_super); + /* For each device we support... */ for (i = 0; i < XFS_GETFSMAP_DEVS; i++) { /* Is this device within the range the user asked for? */ @@ -938,6 +946,7 @@ xfs_getfsmap(
if (tp) xfs_trans_cancel(tp); + sb_end_write(mp->m_super); head->fmh_oflags = FMH_OF_DEV_T; return error; } diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c index 912b42f5fe4a..f45bda9700dc 100644 --- a/fs/xfs/xfs_trans.c +++ b/fs/xfs/xfs_trans.c @@ -309,6 +309,11 @@ xfs_trans_alloc( * * Note the zero-length reservation; this transaction MUST be cancelled * without any dirty data. + * + * Callers should obtain freeze protection to avoid two conflicts with fs + * freezing: (1) having active transactions trip the m_active_trans ASSERTs; + * and (2) grabbing buffers at the same time that freeze is trying to drain + * the buffer LRU list. */ int xfs_trans_alloc_empty(
-
Yang Yingliang