BUG: sleeping function called from invalid context in cgroup_rstat_flush
Subsystems (8)
syzbot
syzbotHello,
syzbot found the following issue on:
HEAD commit: 7c16f0a4ed1c Merge tag 'i2c-for-6.10-rc5' of git://git.ker.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1511528e980000 kernel config: https://syzkaller.appspot.com/x/.config?x=12f98862a3c0c799 dashboard link: https://syzkaller.appspot.com/bug?extid=b7f13b2d0cc156edf61a compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/50560e9024e5/disk-7c16f0a4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/080c27daee72/vmlinux-7c16f0a4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c528e0da4544/bzImage-7c16f0a4.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
BUG: sleeping function called from invalid context at kernel/cgroup/rstat.c:351
in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 17332, name: syz-executor.4preempt_count: 0, expected: 0
RCU nest depth: 1, expected: 0
1 lock held by syz-executor.4/17332:
#0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline] #0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline] #0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: filemap_cachestat mm/filemap.c:4251 [inline] #0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: __do_sys_cachestat mm/filemap.c:4407 [inline] #0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: __se_sys_cachestat+0x3ee/0xbb0 mm/filemap.c:4372
CPU: 1 PID: 17332 Comm: syz-executor.4 Not tainted 6.10.0-rc4-syzkaller-00330-g7c16f0a4ed1c #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114 __might_resched+0x5d4/0x780 kernel/sched/core.c:10196 cgroup_rstat_flush+0x1e/0x50 kernel/cgroup/rstat.c:351 workingset_test_recent+0x48a/0xa90 mm/workingset.c:473 filemap_cachestat mm/filemap.c:4314 [inline] __do_sys_cachestat mm/filemap.c:4407 [inline] __se_sys_cachestat+0x795/0xbb0 mm/filemap.c:4372 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7ff329e7d0a9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ff32ac600c8 EFLAGS: 00000246 ORIG_RAX: 00000000000001c3 RAX: ffffffffffffffda RBX: 00007ff329fb4120 RCX: 00007ff329e7d0a9 RDX: 0000000020000080 RSI: 0000000020000040 RDI: 0000000000000005 RBP: 00007ff329eec074 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 000000000000006e R14: 00007ff329fb4120 R15: 00007ffd3e0ff4a8 </TASK>
---
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Johannes Weiner
maintainerQuoted 31 lines · syzbot
Hello,
syzbot found the following issue on:
HEAD commit: 7c16f0a4ed1c Merge tag 'i2c-for-6.10-rc5' of git://git.ker.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1511528e980000 kernel config: https://syzkaller.appspot.com/x/.config?x=12f98862a3c0c799 dashboard link: https://syzkaller.appspot.com/bug?extid=b7f13b2d0cc156edf61a compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/50560e9024e5/disk-7c16f0a4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/080c27daee72/vmlinux-7c16f0a4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c528e0da4544/bzImage-7c16f0a4.xzIMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by [email protected]BUG: sleeping function called from invalid context at kernel/cgroup/rstat.c:351
in_atomic(): 0,irqs_disabled(): 0,non_block: 0, pid: 17332, name: syz-executor.4preempt_count: 0, expected: 0
RCU nest depth: 1, expected: 0
1 lock held by syz-executor.4/17332:
#0:ffffffff8e333fa0(rcu_read_lock){....}-{1:2}, at:rcu_lock_acquireinclude/linux/rcupdate.h:329[inline] #0:ffffffff8e333fa0(rcu_read_lock){....}-{1:2}, at:rcu_read_lockinclude/linux/rcupdate.h:781[inline] #0:ffffffff8e333fa0(rcu_read_lock){....}-{1:2}, at:filemap_cachestatmm/filemap.c:4251[inline] #0:ffffffff8e333fa0(rcu_read_lock){....}-{1:2}, at:__do_sys_cachestatmm/filemap.c:4407[inline] #0:ffffffff8e333fa0(rcu_read_lock){....}-{1:2}, at:__se_sys_cachestat+0x3ee/0xbb0mm/filemap.c:4372
Quoted 15 lines
CPU: 1 PID: 17332 Comm: syz-executor.4 Not tainted 6.10.0-rc4-syzkaller-00330-g7c16f0a4ed1c #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114 __might_resched+0x5d4/0x780 kernel/sched/core.c:10196 cgroup_rstat_flush+0x1e/0x50 kernel/cgroup/rstat.c:351 workingset_test_recent+0x48a/0xa90 mm/workingset.c:473 filemap_cachestat mm/filemap.c:4314 [inline] __do_sys_cachestat mm/filemap.c:4407 [inline] __se_sys_cachestat+0x795/0xbb0 mm/filemap.c:4372 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f
Ok yeah, cachestat() holds the rcu read lock, so workingset_test_recent() can't do a sleepable rstat flush.
I think the easiest fix would be to flush rstat from the root down (NULL) in filemap_cachestat(), before the rcu section, and add a flag to workingset_test_recent() to forego it. Nhat?
Nhat Pham
reviewerQuoted 49 lines · Johannes Weiner
Quoted 31 lines · syzbot
Hello,
syzbot found the following issue on:
HEAD commit: 7c16f0a4ed1c Merge tag 'i2c-for-6.10-rc5' of git://git.ker.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1511528e980000 kernel config: https://syzkaller.appspot.com/x/.config?x=12f98862a3c0c799 dashboard link: https://syzkaller.appspot.com/bug?extid=b7f13b2d0cc156edf61a compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/50560e9024e5/disk-7c16f0a4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/080c27daee72/vmlinux-7c16f0a4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c528e0da4544/bzImage-7c16f0a4.xzIMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by [email protected]BUG: sleeping function called from invalid context at kernel/cgroup/rstat.c:351
in_atomic(): 0,irqs_disabled(): 0,non_block: 0, pid: 17332, name: syz-executor.4preempt_count: 0, expected: 0
RCU nest depth: 1, expected: 0
1 lock held by syz-executor.4/17332:
#0:ffffffff8e333fa0(rcu_read_lock){....}-{1:2}, at:rcu_lock_acquireinclude/linux/rcupdate.h:329[inline] #0:ffffffff8e333fa0(rcu_read_lock){....}-{1:2}, at:rcu_read_lockinclude/linux/rcupdate.h:781[inline] #0:ffffffff8e333fa0(rcu_read_lock){....}-{1:2}, at:filemap_cachestatmm/filemap.c:4251[inline] #0:ffffffff8e333fa0(rcu_read_lock){....}-{1:2}, at:__do_sys_cachestatmm/filemap.c:4407[inline] #0:ffffffff8e333fa0(rcu_read_lock){....}-{1:2}, at:__se_sys_cachestat+0x3ee/0xbb0mm/filemap.c:4372Quoted 15 lines
CPU: 1 PID: 17332 Comm: syz-executor.4 Not tainted 6.10.0-rc4-syzkaller-00330-g7c16f0a4ed1c #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114 __might_resched+0x5d4/0x780 kernel/sched/core.c:10196 cgroup_rstat_flush+0x1e/0x50 kernel/cgroup/rstat.c:351 workingset_test_recent+0x48a/0xa90 mm/workingset.c:473 filemap_cachestat mm/filemap.c:4314 [inline] __do_sys_cachestat mm/filemap.c:4407 [inline] __se_sys_cachestat+0x795/0xbb0 mm/filemap.c:4372 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f
Quoted 6 lines
Ok yeah,
cachestat()holds the rcu read lock, soworkingset_test_recent()can't do a sleepable rstat flush.I think the easiest fix would be to flush rstat from the root down (NULL) in
filemap_cachestat(), before the rcu section, and add a flag toworkingset_test_recent()to forego it. Nhat?
You're right. I think it's been broken since this commit:
b00684722262 mm: workingset: move the stats flush into workingset_test_recent()
which moves the stats flushing from the refault step (before rcu read lock section) to inside workingset_test_recent(). I believe that's 6.8, 6.9, and 6.10 we need to fix?
The fix sounds reasonable to me :) Let me whip up something real quick.
Nhat Pham
reviewerPATCH 1/1 cachestat: do not flush stats in recency check
In reply to syzbotsyzbot detects that cachestat() is flushing stats, which can sleep, in its RCU read section (see [1]). This is done in the workingset_test_recent() step (which checks if the folio's eviction is recent).
Move the stat flushing step to before the RCU read section of cachestat, and skip stat flushing during the recency check.
[1]: https://lore.kernel.org/cgroups/[email protected]/
--- include/linux/swap.h | 3 ++- mm/filemap.c | 5 ++++- mm/workingset.c | 14 +++++++++++--- 3 files changed, 17 insertions(+), 5 deletions(-)
include/linux/swap.h +2 -1
@@ -354,7 +354,8 @@ static inline swp_entry_t page_swap_entry(struct page *page) }/* linux/mm/workingset.c */ -bool workingset_test_recent (void *shadow,bool file,bool *workingset); +bool workingset_test_recent (void *shadow,bool file,bool *workingset, +bool flush);void workingset_age_nonresident (struct lruvec *lruvec,unsigned long nr_pages);void *workingset_eviction (struct folio *folio,struct mem_cgroup *target_memcg);void workingset_refault (struct folio *folio,void *shadow);
mm/filemap.c +4 -1
@@ -4248,6 +4248,9 @@ static void filemap_cachestat(struct address_space *mapping,XA_STATE (xas, &mapping->i_pages, first_index);struct folio *folio; +/* Flush stats (and potentially sleep) outside the RCU read section. */ +mem_cgroup_flush_stats_ratelimited (NULL ); +rcu_read_lock ();xas_for_each (&xas, folio, last_index) {int order;
@@ -4311,7 +4314,7 @@ static void filemap_cachestat(struct address_space *mapping, goto resched; }#endif -if (workingset_test_recent (shadow, true, &workingset)) +if (workingset_test_recent (shadow, true, &workingset, false)) cs->nr_recently_evicted += nr_pages; goto resched;
mm/workingset.c +11 -3
@@ -412,10 +412,12 @@ void *workingset_eviction(struct folio *folio, struct mem_cgroup *target_memcg)* @file: whether the corresponding folio is from the file lru. * @workingset: where the workingset value unpacked from shadow should * be stored. +* @flush: whether to flush cgroup rstat. * * Return: true if the shadow is for a recently evicted folio; false otherwise. */ -bool workingset_test_recent (void *shadow,bool file,bool *workingset) +bool workingset_test_recent (void *shadow,bool file,bool *workingset, +bool flush) {struct mem_cgroup *eviction_memcg;struct lruvec *eviction_lruvec;
@@ -467,10 +469,16 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset)/* * Flush stats (and potentially sleep) outside the RCU read section. +* +* Note that workingset_test_recent() itself might be called in RCU read +* section (for e.g, in cachestat) - these callers need to skip flushing +* stats (via the flush argument). +* * XXX: With per-memcg flushing and thresholding, is ratelimiting * still needed here? */ -mem_cgroup_flush_stats_ratelimited (eviction_memcg); +if (flush) +mem_cgroup_flush_stats_ratelimited (eviction_memcg); eviction_lruvec =mem_cgroup_lruvec (eviction_memcg, pgdat); refault =atomic_long_read (&eviction_lruvec->nonresident_age);
@@ -558,7 +566,7 @@ void workingset_refault(struct folio *folio, void *shadow)mod_lruvec_state (lruvec,WORKINGSET_REFAULT_BASE + file, nr); -if (!workingset_test_recent (shadow, file, &workingset)) +if (!workingset_test_recent (shadow, file, &workingset, true))return ;folio_set_active (folio);
base-commit: a5c6fededf806aba1ff9b0f01278f7d089da5725
Signature · 1 line
2.43.0
Re: [PATCH] cachestat: do not flush stats in recency check
Quoted 10 lines · Nhat Pham
syzbot detects that
cachestat()is flushing stats, which can sleep, in its RCU read section (see [1]). This is done in theworkingset_test_recent()step (which checks if the folio's eviction is recent).Move the stat flushing step to before the RCU read section of cachestat, and skip stat flushing during the recency check.
Quoted 7 lines
Reported-by [email protected]Debugged-by Johannes Weiner <[email protected]>Suggested-by Johannes Weiner <[email protected]>Signed-off-by Nhat Pham <[email protected]>Fixes b00684722262 ("mm: workingset: move the stats flush into workingset_test_recent()")Cc [email protected] # v6.8+
Re: [PATCH] cachestat: do not flush stats in recency check
In reply to Nhat PhamQuoted 10 lines · Nhat Pham
syzbot detects that
cachestat()is flushing stats, which can sleep, in its RCU read section (see [1]). This is done in theworkingset_test_recent()step (which checks if the folio's eviction is recent).Move the stat flushing step to before the RCU read section of cachestat, and skip stat flushing during the recency check.
Quoted 7 lines
Reported-by [email protected]Debugged-by Johannes Weiner <[email protected]>Suggested-by Johannes Weiner <[email protected]>Signed-off-by Nhat Pham <[email protected]>Fixes b00684722262 ("mm: workingset: move the stats flush into workingset_test_recent()")Cc [email protected] # v6.8+