| Message ID | 20210909060245.2966358-1-yhs@fb.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [bpf-next,v4] bpf: fix lockdep warning triggered by stack_map_get_build_id_offset() | expand |
On Wed, Sep 08, 2021 at 11:02:45PM -0700, Yonghong Song wrote: > Current bpf-next bpf selftest "get_stack_raw_tp" triggered the warning: > > [ 1411.304463] WARNING: CPU: 3 PID: 140 at include/linux/mmap_lock.h:164 find_vma+0x47/0xa0 > [ 1411.304469] Modules linked in: bpf_testmod(O) [last unloaded: bpf_testmod] > [ 1411.304476] CPU: 3 PID: 140 Comm: systemd-journal Tainted: G W O 5.14.0+ #53 > [ 1411.304479] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 > [ 1411.304481] RIP: 0010:find_vma+0x47/0xa0 > [ 1411.304484] Code: de 48 89 ef e8 ba f5 fe ff 48 85 c0 74 2e 48 83 c4 08 5b 5d c3 48 8d bf 28 01 00 00 be ff ff ff ff e8 2d 9f d8 00 85 c0 75 d4 <0f> 0b 48 89 de 48 8 > [ 1411.304487] RSP: 0018:ffffabd440403db8 EFLAGS: 00010246 > [ 1411.304490] RAX: 0000000000000000 RBX: 00007f00ad80a0e0 RCX: 0000000000000000 > [ 1411.304492] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e > [ 1411.304494] RBP: ffff9cf5c2f50000 R08: ffff9cf5c3eb25d8 R09: 00000000fffffffe > [ 1411.304496] R10: 0000000000000001 R11: 00000000ef974e19 R12: ffff9cf5c39ae0e0 > [ 1411.304498] R13: 0000000000000000 R14: 0000000000000000 R15: ffff9cf5c39ae0e0 > [ 1411.304501] FS: 00007f00ae754780(0000) GS:ffff9cf5fba00000(0000) knlGS:0000000000000000 > [ 1411.304504] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 1411.304506] CR2: 000000003e34343c CR3: 0000000103a98005 CR4: 0000000000370ee0 > [ 1411.304508] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 1411.304510] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 1411.304512] Call Trace: > [ 1411.304517] stack_map_get_build_id_offset+0x17c/0x260 > [ 1411.304528] __bpf_get_stack+0x18f/0x230 > [ 1411.304541] bpf_get_stack_raw_tp+0x5a/0x70 > [ 1411.305752] RAX: 0000000000000000 RBX: 5541f689495641d7 RCX: 0000000000000000 > [ 1411.305756] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e > [ 1411.305758] RBP: ffff9cf5c02b2f40 R08: ffff9cf5ca7606c0 R09: ffffcbd43ee02c04 > [ 1411.306978] bpf_prog_32007c34f7726d29_bpf_prog1+0xaf/0xd9c > [ 1411.307861] R10: 0000000000000001 R11: 0000000000000044 R12: ffff9cf5c2ef60e0 > [ 1411.307865] R13: 0000000000000005 R14: 0000000000000000 R15: ffff9cf5c2ef6108 > [ 1411.309074] bpf_trace_run2+0x8f/0x1a0 > [ 1411.309891] FS: 00007ff485141700(0000) GS:ffff9cf5fae00000(0000) knlGS:0000000000000000 > [ 1411.309896] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 1411.311221] syscall_trace_enter.isra.20+0x161/0x1f0 > [ 1411.311600] CR2: 00007ff48514d90e CR3: 0000000107114001 CR4: 0000000000370ef0 > [ 1411.312291] do_syscall_64+0x15/0x80 > [ 1411.312941] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 1411.313803] entry_SYSCALL_64_after_hwframe+0x44/0xae > [ 1411.314223] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 1411.315082] RIP: 0033:0x7f00ad80a0e0 > [ 1411.315626] Call Trace: > [ 1411.315632] stack_map_get_build_id_offset+0x17c/0x260 > > To reproduce, first build `test_progs` binary: > make -C tools/testing/selftests/bpf -j60 > and then run the binary at tools/testing/selftests/bpf directory: > ./test_progs -t get_stack_raw_tp > > The warning is due to commit 5b78ed24e8ec("mm/pagemap: add mmap_assert_locked() > annotations to find_vma*()") which added mmap_assert_locked() in find_vma() function. > The mmap_assert_locked() function asserts that mm->mmap_lock needs to be held. But this > is not the case for bpf_get_stack() or bpf_get_stackid() helper (kernel/bpf/stackmap.c), > which uses mmap_read_trylock_non_owner() instead. Since mm->mmap_lock is not held > in bpf_get_stack[id]() use case, the above warning is emitted during test run. > > This patch fixed the issue by (1). using mmap_read_trylock() instead of > mmap_read_trylock_non_owner() to satisfy lockdep checking in find_vma(), > and (2). droping lockdep for mmap_lock right before the irq_work_queue(). > > Cc: Luigi Rizzo <lrizzo@google.com> > Suggested-by: Jason Gunthorpe <jgg@ziepe.ca> > Fixes: 5b78ed24e8ec("mm/pagemap: add mmap_assert_locked() annotations to find_vma*()") > Signed-off-by: Yonghong Song <yhs@fb.com> > kernel/bpf/stackmap.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > index e8eefdf8cf3e..7b7500a3724b 100644 > +++ b/kernel/bpf/stackmap.c > @@ -179,7 +179,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > * with build_id. > */ > if (!user || !current || !current->mm || irq_work_busy || > - !mmap_read_trylock_non_owner(current->mm)) { > + !mmap_read_trylock(current->mm)) { This was the only caller of mmap_read_trylock_non_owner(), so please delete it too Jason
On Wed, Sep 08, 2021 at 11:02:45PM -0700, Yonghong Song wrote: > @@ -204,9 +204,10 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > } > > if (!work) { > - mmap_read_unlock_non_owner(current->mm); > + mmap_read_unlock(current->mm); > } else { > work->mm = current->mm; > + rwsem_release(¤t->mm->mmap_lock.dep_map, _RET_IP_); > irq_work_queue(&work->irq_work); This needs a comment before the rwsem_release(). Something like: /* * The lock will be released once we're out of interrupt * context. Tell lockdep that we've released it now so * it doesn't complain that we forgot to release it. */
On 9/9/21 5:34 AM, Jason Gunthorpe wrote: > On Wed, Sep 08, 2021 at 11:02:45PM -0700, Yonghong Song wrote: >> Current bpf-next bpf selftest "get_stack_raw_tp" triggered the warning: >> >> [ 1411.304463] WARNING: CPU: 3 PID: 140 at include/linux/mmap_lock.h:164 find_vma+0x47/0xa0 >> [ 1411.304469] Modules linked in: bpf_testmod(O) [last unloaded: bpf_testmod] >> [ 1411.304476] CPU: 3 PID: 140 Comm: systemd-journal Tainted: G W O 5.14.0+ #53 >> [ 1411.304479] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 >> [ 1411.304481] RIP: 0010:find_vma+0x47/0xa0 >> [ 1411.304484] Code: de 48 89 ef e8 ba f5 fe ff 48 85 c0 74 2e 48 83 c4 08 5b 5d c3 48 8d bf 28 01 00 00 be ff ff ff ff e8 2d 9f d8 00 85 c0 75 d4 <0f> 0b 48 89 de 48 8 >> [ 1411.304487] RSP: 0018:ffffabd440403db8 EFLAGS: 00010246 >> [ 1411.304490] RAX: 0000000000000000 RBX: 00007f00ad80a0e0 RCX: 0000000000000000 >> [ 1411.304492] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e >> [ 1411.304494] RBP: ffff9cf5c2f50000 R08: ffff9cf5c3eb25d8 R09: 00000000fffffffe >> [ 1411.304496] R10: 0000000000000001 R11: 00000000ef974e19 R12: ffff9cf5c39ae0e0 >> [ 1411.304498] R13: 0000000000000000 R14: 0000000000000000 R15: ffff9cf5c39ae0e0 >> [ 1411.304501] FS: 00007f00ae754780(0000) GS:ffff9cf5fba00000(0000) knlGS:0000000000000000 >> [ 1411.304504] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> [ 1411.304506] CR2: 000000003e34343c CR3: 0000000103a98005 CR4: 0000000000370ee0 >> [ 1411.304508] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> [ 1411.304510] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> [ 1411.304512] Call Trace: >> [ 1411.304517] stack_map_get_build_id_offset+0x17c/0x260 >> [ 1411.304528] __bpf_get_stack+0x18f/0x230 >> [ 1411.304541] bpf_get_stack_raw_tp+0x5a/0x70 >> [ 1411.305752] RAX: 0000000000000000 RBX: 5541f689495641d7 RCX: 0000000000000000 >> [ 1411.305756] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e >> [ 1411.305758] RBP: ffff9cf5c02b2f40 R08: ffff9cf5ca7606c0 R09: ffffcbd43ee02c04 >> [ 1411.306978] bpf_prog_32007c34f7726d29_bpf_prog1+0xaf/0xd9c >> [ 1411.307861] R10: 0000000000000001 R11: 0000000000000044 R12: ffff9cf5c2ef60e0 >> [ 1411.307865] R13: 0000000000000005 R14: 0000000000000000 R15: ffff9cf5c2ef6108 >> [ 1411.309074] bpf_trace_run2+0x8f/0x1a0 >> [ 1411.309891] FS: 00007ff485141700(0000) GS:ffff9cf5fae00000(0000) knlGS:0000000000000000 >> [ 1411.309896] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> [ 1411.311221] syscall_trace_enter.isra.20+0x161/0x1f0 >> [ 1411.311600] CR2: 00007ff48514d90e CR3: 0000000107114001 CR4: 0000000000370ef0 >> [ 1411.312291] do_syscall_64+0x15/0x80 >> [ 1411.312941] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> [ 1411.313803] entry_SYSCALL_64_after_hwframe+0x44/0xae >> [ 1411.314223] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> [ 1411.315082] RIP: 0033:0x7f00ad80a0e0 >> [ 1411.315626] Call Trace: >> [ 1411.315632] stack_map_get_build_id_offset+0x17c/0x260 >> >> To reproduce, first build `test_progs` binary: >> make -C tools/testing/selftests/bpf -j60 >> and then run the binary at tools/testing/selftests/bpf directory: >> ./test_progs -t get_stack_raw_tp >> >> The warning is due to commit 5b78ed24e8ec("mm/pagemap: add mmap_assert_locked() >> annotations to find_vma*()") which added mmap_assert_locked() in find_vma() function. >> The mmap_assert_locked() function asserts that mm->mmap_lock needs to be held. But this >> is not the case for bpf_get_stack() or bpf_get_stackid() helper (kernel/bpf/stackmap.c), >> which uses mmap_read_trylock_non_owner() instead. Since mm->mmap_lock is not held >> in bpf_get_stack[id]() use case, the above warning is emitted during test run. >> >> This patch fixed the issue by (1). using mmap_read_trylock() instead of >> mmap_read_trylock_non_owner() to satisfy lockdep checking in find_vma(), >> and (2). droping lockdep for mmap_lock right before the irq_work_queue(). >> >> Cc: Luigi Rizzo <lrizzo@google.com> >> Suggested-by: Jason Gunthorpe <jgg@ziepe.ca> >> Fixes: 5b78ed24e8ec("mm/pagemap: add mmap_assert_locked() annotations to find_vma*()") >> Signed-off-by: Yonghong Song <yhs@fb.com> >> kernel/bpf/stackmap.c | 5 +++-- >> 1 file changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c >> index e8eefdf8cf3e..7b7500a3724b 100644 >> +++ b/kernel/bpf/stackmap.c >> @@ -179,7 +179,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, >> * with build_id. >> */ >> if (!user || !current || !current->mm || irq_work_busy || >> - !mmap_read_trylock_non_owner(current->mm)) { >> + !mmap_read_trylock(current->mm)) { > > This was the only caller of mmap_read_trylock_non_owner(), so please > delete it too Thanks. Will do. > > Jason >
On 9/9/21 6:33 AM, Matthew Wilcox wrote: > On Wed, Sep 08, 2021 at 11:02:45PM -0700, Yonghong Song wrote: >> @@ -204,9 +204,10 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, >> } >> >> if (!work) { >> - mmap_read_unlock_non_owner(current->mm); >> + mmap_read_unlock(current->mm); >> } else { >> work->mm = current->mm; >> + rwsem_release(¤t->mm->mmap_lock.dep_map, _RET_IP_); >> irq_work_queue(&work->irq_work); > > This needs a comment before the rwsem_release(). Something like: > > /* > * The lock will be released once we're out of interrupt > * context. Tell lockdep that we've released it now so > * it doesn't complain that we forgot to release it. > */ Thanks! Will add it in the next revision.
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index e8eefdf8cf3e..7b7500a3724b 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -179,7 +179,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, * with build_id. */ if (!user || !current || !current->mm || irq_work_busy || - !mmap_read_trylock_non_owner(current->mm)) { + !mmap_read_trylock(current->mm)) { /* cannot access current->mm, fall back to ips */ for (i = 0; i < trace_nr; i++) { id_offs[i].status = BPF_STACK_BUILD_ID_IP; @@ -204,9 +204,10 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, } if (!work) { - mmap_read_unlock_non_owner(current->mm); + mmap_read_unlock(current->mm); } else { work->mm = current->mm; + rwsem_release(¤t->mm->mmap_lock.dep_map, _RET_IP_); irq_work_queue(&work->irq_work); } }
Current bpf-next bpf selftest "get_stack_raw_tp" triggered the warning: [ 1411.304463] WARNING: CPU: 3 PID: 140 at include/linux/mmap_lock.h:164 find_vma+0x47/0xa0 [ 1411.304469] Modules linked in: bpf_testmod(O) [last unloaded: bpf_testmod] [ 1411.304476] CPU: 3 PID: 140 Comm: systemd-journal Tainted: G W O 5.14.0+ #53 [ 1411.304479] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 [ 1411.304481] RIP: 0010:find_vma+0x47/0xa0 [ 1411.304484] Code: de 48 89 ef e8 ba f5 fe ff 48 85 c0 74 2e 48 83 c4 08 5b 5d c3 48 8d bf 28 01 00 00 be ff ff ff ff e8 2d 9f d8 00 85 c0 75 d4 <0f> 0b 48 89 de 48 8 [ 1411.304487] RSP: 0018:ffffabd440403db8 EFLAGS: 00010246 [ 1411.304490] RAX: 0000000000000000 RBX: 00007f00ad80a0e0 RCX: 0000000000000000 [ 1411.304492] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e [ 1411.304494] RBP: ffff9cf5c2f50000 R08: ffff9cf5c3eb25d8 R09: 00000000fffffffe [ 1411.304496] R10: 0000000000000001 R11: 00000000ef974e19 R12: ffff9cf5c39ae0e0 [ 1411.304498] R13: 0000000000000000 R14: 0000000000000000 R15: ffff9cf5c39ae0e0 [ 1411.304501] FS: 00007f00ae754780(0000) GS:ffff9cf5fba00000(0000) knlGS:0000000000000000 [ 1411.304504] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1411.304506] CR2: 000000003e34343c CR3: 0000000103a98005 CR4: 0000000000370ee0 [ 1411.304508] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1411.304510] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 1411.304512] Call Trace: [ 1411.304517] stack_map_get_build_id_offset+0x17c/0x260 [ 1411.304528] __bpf_get_stack+0x18f/0x230 [ 1411.304541] bpf_get_stack_raw_tp+0x5a/0x70 [ 1411.305752] RAX: 0000000000000000 RBX: 5541f689495641d7 RCX: 0000000000000000 [ 1411.305756] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e [ 1411.305758] RBP: ffff9cf5c02b2f40 R08: ffff9cf5ca7606c0 R09: ffffcbd43ee02c04 [ 1411.306978] bpf_prog_32007c34f7726d29_bpf_prog1+0xaf/0xd9c [ 1411.307861] R10: 0000000000000001 R11: 0000000000000044 R12: ffff9cf5c2ef60e0 [ 1411.307865] R13: 0000000000000005 R14: 0000000000000000 R15: ffff9cf5c2ef6108 [ 1411.309074] bpf_trace_run2+0x8f/0x1a0 [ 1411.309891] FS: 00007ff485141700(0000) GS:ffff9cf5fae00000(0000) knlGS:0000000000000000 [ 1411.309896] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1411.311221] syscall_trace_enter.isra.20+0x161/0x1f0 [ 1411.311600] CR2: 00007ff48514d90e CR3: 0000000107114001 CR4: 0000000000370ef0 [ 1411.312291] do_syscall_64+0x15/0x80 [ 1411.312941] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1411.313803] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 1411.314223] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 1411.315082] RIP: 0033:0x7f00ad80a0e0 [ 1411.315626] Call Trace: [ 1411.315632] stack_map_get_build_id_offset+0x17c/0x260 To reproduce, first build `test_progs` binary: make -C tools/testing/selftests/bpf -j60 and then run the binary at tools/testing/selftests/bpf directory: ./test_progs -t get_stack_raw_tp The warning is due to commit 5b78ed24e8ec("mm/pagemap: add mmap_assert_locked() annotations to find_vma*()") which added mmap_assert_locked() in find_vma() function. The mmap_assert_locked() function asserts that mm->mmap_lock needs to be held. But this is not the case for bpf_get_stack() or bpf_get_stackid() helper (kernel/bpf/stackmap.c), which uses mmap_read_trylock_non_owner() instead. Since mm->mmap_lock is not held in bpf_get_stack[id]() use case, the above warning is emitted during test run. This patch fixed the issue by (1). using mmap_read_trylock() instead of mmap_read_trylock_non_owner() to satisfy lockdep checking in find_vma(), and (2). droping lockdep for mmap_lock right before the irq_work_queue(). Cc: Luigi Rizzo <lrizzo@google.com> Suggested-by: Jason Gunthorpe <jgg@ziepe.ca> Fixes: 5b78ed24e8ec("mm/pagemap: add mmap_assert_locked() annotations to find_vma*()") Signed-off-by: Yonghong Song <yhs@fb.com> --- kernel/bpf/stackmap.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)