* Race in mm/ksm.c @ 2022-07-21 15:58 Abhishek Shah 2022-07-22 1:57 ` Kefeng Wang 0 siblings, 1 reply; 5+ messages in thread From: Abhishek Shah @ 2022-07-21 15:58 UTC (permalink / raw) To: akpm, linux-mm, linux-kernel; +Cc: Gabriel Ryan [-- Attachment #1: Type: text/plain, Size: 2559 bytes --] Dear Kernel Maintainers, We found a race in mm/ksm.c. During the execution of the function *__ksm_run* which uses variable *ksm_run* to decide the list insertion point, the variable *ksm_run* can be concurrently modified in the function *run_store*, which we thought could be undesirable since “KSM pages in newly forked mms can be missed” (See comment here: https://elixir.bootlin.com/linux/v5.18-rc5/source/mm/ksm.c#L2498). We would also like your thoughts on the security impact given it is a TOCTOU bug. We provide more details below including the trace and reproducing test cases. *Trace* BUG: KCSAN: data-race in __ksm_enter / run_store write to 0xffffffff881edae0 of 8 bytes by task 6542 on cpu 0: run_store+0x19a/0x2d0 mm/ksm.c:2897 kobj_attr_store+0x44/0x60 lib/kobject.c:824 sysfs_kf_write+0x16f/0x1a0 fs/sysfs/file.c:136 kernfs_fop_write_iter+0x2ae/0x370 fs/kernfs/file.c:291 call_write_iter include/linux/fs.h:2050 [inline] new_sync_write fs/read_write.c:504 [inline] vfs_write+0x779/0x900 fs/read_write.c:591 ksys_write+0xde/0x190 fs/read_write.c:644 __do_sys_write fs/read_write.c:656 [inline] __se_sys_write fs/read_write.c:653 [inline] __x64_sys_write+0x43/0x50 fs/read_write.c:653 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffffffff881edae0 of 8 bytes by task 6541 on cpu 1: __ksm_enter+0x114/0x260 mm/ksm.c:2501 ksm_madvise+0x291/0x350 mm/ksm.c:2451 madvise_vma_behavior mm/madvise.c:1039 [inline] madvise_walk_vmas mm/madvise.c:1221 [inline] do_madvise+0x656/0xeb0 mm/madvise.c:1399 __do_sys_madvise mm/madvise.c:1412 [inline] __se_sys_madvise mm/madvise.c:1410 [inline] __x64_sys_madvise+0x64/0x70 mm/madvise.c:1410 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 6541 Comm: syz-executor2-n Not tainted 5.18.0-rc5+ #107 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 --------------------- *Inputs * Input CPU 0: r0 = openat$sysctl(0xffffff9c, &(0x7f0000000100)='/sys/kernel/mm/ksm/run\x00', 0x1, 0x0) write$sysctl(r0, &(0x7f0000000000)='2\x00', 0x2) Input CPU 1: madvise(&(0x7f0000ffc000/0x4000)=nil, 0x4000, 0xc) mlock2(&(0x7f0000ffe000/0x2000)=nil, 0x2000, 0x0) madvise(&(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x12) clone(0x0, 0x0, 0x0, 0x0, 0x0) [-- Attachment #2: Type: text/html, Size: 3412 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Race in mm/ksm.c 2022-07-21 15:58 Race in mm/ksm.c Abhishek Shah @ 2022-07-22 1:57 ` Kefeng Wang 2022-08-02 11:44 ` Gabriel Ryan 0 siblings, 1 reply; 5+ messages in thread From: Kefeng Wang @ 2022-07-22 1:57 UTC (permalink / raw) To: abhishek.shah, akpm, linux-mm, linux-kernel; +Cc: Gabriel Ryan [-- Attachment #1: Type: text/plain, Size: 4198 bytes --] On 2022/7/21 23:58, Abhishek Shah wrote: > Dear Kernel Maintainers, > > We found a race in mm/ksm.c. During the execution of the function > /__ksm_run/ which uses variable /ksm_run/ to decide the list insertion > point, the variable /ksm_run/ can be concurrently modified in the > function /run_store/, which we thought could be undesirable since “KSM > pages in newly forked mms can be missed” (See comment here: > https://elixir.bootlin.com/linux/v5.18-rc5/source/mm/ksm.c#L2498 > <https://elixir.bootlin.com/linux/v5.18-rc5/source/mm/ksm.c#L2498>). > We would also like your thoughts on the security impact given it is a > TOCTOU bug. > > We provide more details below including the trace and reproducing > test cases. Hello， could the following changes to avoid the data-race issue？ diff --git a/mm/ksm.c b/mm/ksm.c index 54f78c9eecae..f072753cbb3a 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2497,6 +2497,7 @@ int __ksm_enter(struct mm_struct *mm) { struct mm_slot *mm_slot; int needs_wakeup; + bool ksm_run_merge; mm_slot = alloc_mm_slot(); if (!mm_slot) @@ -2505,6 +2506,10 @@ int __ksm_enter(struct mm_struct *mm) /* Check ksm_run too? Would need tighter locking */ needs_wakeup = list_empty(&ksm_mm_head.mm_list); + mutex_lock(&ksm_thread_mutex); + ksm_run_unmerge = !!(ksm_run & KSM_RUN_UNMERGE); + mutex_unlock(&ksm_thread_mutex); + spin_lock(&ksm_mmlist_lock); insert_to_mm_slots_hash(mm, mm_slot); /* @@ -2517,7 +2522,7 @@ int __ksm_enter(struct mm_struct *mm) * scanning cursor, otherwise KSM pages in newly forked mms will be * missed: then we might as well insert at the end of the list. */ - if (ksm_run & KSM_RUN_UNMERGE) + if (ksm_run_unmerge) list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list); else list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); > > > *Trace* > BUG: KCSAN: data-race in __ksm_enter / run_store > write to 0xffffffff881edae0 of 8 bytes by task 6542 on cpu 0: > run_store+0x19a/0x2d0 mm/ksm.c:2897 > kobj_attr_store+0x44/0x60 lib/kobject.c:824 > sysfs_kf_write+0x16f/0x1a0 fs/sysfs/file.c:136 > kernfs_fop_write_iter+0x2ae/0x370 fs/kernfs/file.c:291 > call_write_iter include/linux/fs.h:2050 [inline] > new_sync_write fs/read_write.c:504 [inline] > vfs_write+0x779/0x900 fs/read_write.c:591 > ksys_write+0xde/0x190 fs/read_write.c:644 > __do_sys_write fs/read_write.c:656 [inline] > __se_sys_write fs/read_write.c:653 [inline] > __x64_sys_write+0x43/0x50 fs/read_write.c:653 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > read to 0xffffffff881edae0 of 8 bytes by task 6541 on cpu 1: > __ksm_enter+0x114/0x260 mm/ksm.c:2501 > ksm_madvise+0x291/0x350 mm/ksm.c:2451 > madvise_vma_behavior mm/madvise.c:1039 [inline] > madvise_walk_vmas mm/madvise.c:1221 [inline] > do_madvise+0x656/0xeb0 mm/madvise.c:1399 > __do_sys_madvise mm/madvise.c:1412 [inline] > __se_sys_madvise mm/madvise.c:1410 [inline] > __x64_sys_madvise+0x64/0x70 mm/madvise.c:1410 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 PID: 6541 Comm: syz-executor2-n Not tainted 5.18.0-rc5+ #107 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 > 04/01/2014 > --------------------- > *Inputs * > Input CPU 0: > r0 = openat$sysctl(0xffffff9c, > &(0x7f0000000100)='/sys/kernel/mm/ksm/run\x00', 0x1, 0x0) > write$sysctl(r0, &(0x7f0000000000)='2\x00', 0x2) > > Input CPU 1: > madvise(&(0x7f0000ffc000/0x4000)=nil, 0x4000, 0xc) > mlock2(&(0x7f0000ffe000/0x2000)=nil, 0x2000, 0x0) > madvise(&(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x12) > clone(0x0, 0x0, 0x0, 0x0, 0x0) [-- Attachment #2: Type: text/html, Size: 6765 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Race in mm/ksm.c 2022-07-22 1:57 ` Kefeng Wang @ 2022-08-02 11:44 ` Gabriel Ryan 2022-08-02 12:18 ` Kefeng Wang 0 siblings, 1 reply; 5+ messages in thread From: Gabriel Ryan @ 2022-08-02 11:44 UTC (permalink / raw) To: Kefeng Wang; +Cc: abhishek.shah, akpm, linux-mm, linux-kernel [-- Attachment #1: Type: text/plain, Size: 4269 bytes --] Confirmed. Thanks for the quick response and apologies for the delay! Best, Gabe On Thu, Jul 21, 2022 at 9:57 PM Kefeng Wang <wangkefeng.wang@huawei.com> wrote: > > On 2022/7/21 23:58, Abhishek Shah wrote: > > Dear Kernel Maintainers, > > We found a race in mm/ksm.c. During the execution of the function > *__ksm_run* which uses variable *ksm_run* to decide the list insertion > point, the variable *ksm_run* can be concurrently modified in the > function *run_store*, which we thought could be undesirable since “KSM > pages in newly forked mms can be missed” (See comment here: > https://elixir.bootlin.com/linux/v5.18-rc5/source/mm/ksm.c#L2498). We > would also like your thoughts on the security impact given it is a TOCTOU > bug. > > We provide more details below including the trace and reproducing > test cases. > > > Hello， could the following changes to avoid the data-race issue？ > > diff --git a/mm/ksm.c b/mm/ksm.c > index 54f78c9eecae..f072753cbb3a 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -2497,6 +2497,7 @@ int __ksm_enter(struct mm_struct *mm) > { > struct mm_slot *mm_slot; > int needs_wakeup; > + bool ksm_run_merge; > > mm_slot = alloc_mm_slot(); > if (!mm_slot) > @@ -2505,6 +2506,10 @@ int __ksm_enter(struct mm_struct *mm) > /* Check ksm_run too? Would need tighter locking */ > needs_wakeup = list_empty(&ksm_mm_head.mm_list); > > + mutex_lock(&ksm_thread_mutex); > + ksm_run_unmerge = !!(ksm_run & KSM_RUN_UNMERGE); > + mutex_unlock(&ksm_thread_mutex); > + > spin_lock(&ksm_mmlist_lock); > insert_to_mm_slots_hash(mm, mm_slot); > /* > @@ -2517,7 +2522,7 @@ int __ksm_enter(struct mm_struct *mm) > * scanning cursor, otherwise KSM pages in newly forked mms will be > * missed: then we might as well insert at the end of the list. > */ > - if (ksm_run & KSM_RUN_UNMERGE) > + if (ksm_run_unmerge) > list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list); > else > list_add_tail(&mm_slot->mm_list, > &ksm_scan.mm_slot->mm_list); > > > > > *Trace* > BUG: KCSAN: data-race in __ksm_enter / run_store > write to 0xffffffff881edae0 of 8 bytes by task 6542 on cpu 0: > run_store+0x19a/0x2d0 mm/ksm.c:2897 > kobj_attr_store+0x44/0x60 lib/kobject.c:824 > sysfs_kf_write+0x16f/0x1a0 fs/sysfs/file.c:136 > kernfs_fop_write_iter+0x2ae/0x370 fs/kernfs/file.c:291 > call_write_iter include/linux/fs.h:2050 [inline] > new_sync_write fs/read_write.c:504 [inline] > vfs_write+0x779/0x900 fs/read_write.c:591 > ksys_write+0xde/0x190 fs/read_write.c:644 > __do_sys_write fs/read_write.c:656 [inline] > __se_sys_write fs/read_write.c:653 [inline] > __x64_sys_write+0x43/0x50 fs/read_write.c:653 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > read to 0xffffffff881edae0 of 8 bytes by task 6541 on cpu 1: > __ksm_enter+0x114/0x260 mm/ksm.c:2501 > ksm_madvise+0x291/0x350 mm/ksm.c:2451 > madvise_vma_behavior mm/madvise.c:1039 [inline] > madvise_walk_vmas mm/madvise.c:1221 [inline] > do_madvise+0x656/0xeb0 mm/madvise.c:1399 > __do_sys_madvise mm/madvise.c:1412 [inline] > __se_sys_madvise mm/madvise.c:1410 [inline] > __x64_sys_madvise+0x64/0x70 mm/madvise.c:1410 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 PID: 6541 Comm: syz-executor2-n Not tainted 5.18.0-rc5+ #107 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 > 04/01/2014 > --------------------- > *Inputs * > Input CPU 0: > r0 = openat$sysctl(0xffffff9c, > &(0x7f0000000100)='/sys/kernel/mm/ksm/run\x00', 0x1, 0x0) > write$sysctl(r0, &(0x7f0000000000)='2\x00', 0x2) > > Input CPU 1: > madvise(&(0x7f0000ffc000/0x4000)=nil, 0x4000, 0xc) > mlock2(&(0x7f0000ffe000/0x2000)=nil, 0x2000, 0x0) > madvise(&(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x12) > clone(0x0, 0x0, 0x0, 0x0, 0x0) > > [-- Attachment #2: Type: text/html, Size: 6670 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Race in mm/ksm.c 2022-08-02 11:44 ` Gabriel Ryan @ 2022-08-02 12:18 ` Kefeng Wang 2022-08-02 12:33 ` Gabriel Ryan 0 siblings, 1 reply; 5+ messages in thread From: Kefeng Wang @ 2022-08-02 12:18 UTC (permalink / raw) To: Gabriel Ryan; +Cc: abhishek.shah, akpm, linux-mm, linux-kernel [-- Attachment #1: Type: text/plain, Size: 5050 bytes --] On 2022/8/2 19:44, Gabriel Ryan wrote: > Confirmed. It means that the following changes could fix the issue, right? If so, I will send a formal patch with your report and test, thanks. > > Thanks for the quick response and apologies for the delay! > > Best, > > Gabe > > On Thu, Jul 21, 2022 at 9:57 PM Kefeng Wang > <wangkefeng.wang@huawei.com> wrote: > > > On 2022/7/21 23:58, Abhishek Shah wrote: >> Dear Kernel Maintainers, >> >> We found a race in mm/ksm.c. During the execution of the function >> /__ksm_run/ which uses variable /ksm_run/ to decide the list >> insertion point, the variable /ksm_run/ can be concurrently >> modified in the function /run_store/, which we thought could be >> undesirable since “KSM pages in newly forked mms can be missed” >> (See comment here: >> https://elixir.bootlin.com/linux/v5.18-rc5/source/mm/ksm.c#L2498 >> <https://elixir.bootlin.com/linux/v5.18-rc5/source/mm/ksm.c#L2498>). >> We would also like your thoughts on the security impact given it >> is a TOCTOU bug. >> >> We provide more details below including the trace and reproducing >> test cases. > > > Hello， could the following changes to avoid the data-race issue？ > > diff --git a/mm/ksm.c b/mm/ksm.c > index 54f78c9eecae..f072753cbb3a 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -2497,6 +2497,7 @@ int __ksm_enter(struct mm_struct *mm) > { > struct mm_slot *mm_slot; > int needs_wakeup; > + bool ksm_run_merge; > > mm_slot = alloc_mm_slot(); > if (!mm_slot) > @@ -2505,6 +2506,10 @@ int __ksm_enter(struct mm_struct *mm) > /* Check ksm_run too? Would need tighter locking */ > needs_wakeup = list_empty(&ksm_mm_head.mm_list); > > + mutex_lock(&ksm_thread_mutex); > + ksm_run_unmerge = !!(ksm_run & KSM_RUN_UNMERGE); > + mutex_unlock(&ksm_thread_mutex); > + > spin_lock(&ksm_mmlist_lock); > insert_to_mm_slots_hash(mm, mm_slot); > /* > @@ -2517,7 +2522,7 @@ int __ksm_enter(struct mm_struct *mm) > * scanning cursor, otherwise KSM pages in newly forked > mms will be > * missed: then we might as well insert at the end of the > list. > */ > - if (ksm_run & KSM_RUN_UNMERGE) > + if (ksm_run_unmerge) > list_add_tail(&mm_slot->mm_list, > &ksm_mm_head.mm_list); > else > list_add_tail(&mm_slot->mm_list, > &ksm_scan.mm_slot->mm_list); > > >> >> >> *Trace* >> BUG: KCSAN: data-race in __ksm_enter / run_store >> write to 0xffffffff881edae0 of 8 bytes by task 6542 on cpu 0: >> run_store+0x19a/0x2d0 mm/ksm.c:2897 >> kobj_attr_store+0x44/0x60 lib/kobject.c:824 >> sysfs_kf_write+0x16f/0x1a0 fs/sysfs/file.c:136 >> kernfs_fop_write_iter+0x2ae/0x370 fs/kernfs/file.c:291 >> call_write_iter include/linux/fs.h:2050 [inline] >> new_sync_write fs/read_write.c:504 [inline] >> vfs_write+0x779/0x900 fs/read_write.c:591 >> ksys_write+0xde/0x190 fs/read_write.c:644 >> __do_sys_write fs/read_write.c:656 [inline] >> __se_sys_write fs/read_write.c:653 [inline] >> __x64_sys_write+0x43/0x50 fs/read_write.c:653 >> do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 >> entry_SYSCALL_64_after_hwframe+0x44/0xae >> >> read to 0xffffffff881edae0 of 8 bytes by task 6541 on cpu 1: >> __ksm_enter+0x114/0x260 mm/ksm.c:2501 >> ksm_madvise+0x291/0x350 mm/ksm.c:2451 >> madvise_vma_behavior mm/madvise.c:1039 [inline] >> madvise_walk_vmas mm/madvise.c:1221 [inline] >> do_madvise+0x656/0xeb0 mm/madvise.c:1399 >> __do_sys_madvise mm/madvise.c:1412 [inline] >> __se_sys_madvise mm/madvise.c:1410 [inline] >> __x64_sys_madvise+0x64/0x70 mm/madvise.c:1410 >> do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 >> entry_SYSCALL_64_after_hwframe+0x44/0xae >> >> Reported by Kernel Concurrency Sanitizer on: >> CPU: 1 PID: 6541 Comm: syz-executor2-n Not tainted 5.18.0-rc5+ #107 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS >> 1.15.0-1 04/01/2014 >> --------------------- >> *Inputs * >> Input CPU 0: >> r0 = openat$sysctl(0xffffff9c, >> &(0x7f0000000100)='/sys/kernel/mm/ksm/run\x00', 0x1, 0x0) >> write$sysctl(r0, &(0x7f0000000000)='2\x00', 0x2) >> >> Input CPU 1: >> madvise(&(0x7f0000ffc000/0x4000)=nil, 0x4000, 0xc) >> mlock2(&(0x7f0000ffe000/0x2000)=nil, 0x2000, 0x0) >> madvise(&(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x12) >> clone(0x0, 0x0, 0x0, 0x0, 0x0) > [-- Attachment #2: Type: text/html, Size: 8855 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Race in mm/ksm.c 2022-08-02 12:18 ` Kefeng Wang @ 2022-08-02 12:33 ` Gabriel Ryan 0 siblings, 0 replies; 5+ messages in thread From: Gabriel Ryan @ 2022-08-02 12:33 UTC (permalink / raw) To: Kefeng Wang; +Cc: abhishek.shah, akpm, linux-mm, linux-kernel [-- Attachment #1: Type: text/plain, Size: 5011 bytes --] Yes, we are unable to trigger the reported race after applying your patch, and by inspection the patch appears to have fixed the issue by extending ksm_thread_mutex to cover the ksm_run flag check in __ksm_enter. We have also contacted the kernel security team since the race may have security implications. Thanks, Gabe On Tue, Aug 2, 2022 at 8:18 AM Kefeng Wang <wangkefeng.wang@huawei.com> wrote: > > On 2022/8/2 19:44, Gabriel Ryan wrote: > > Confirmed. > > It means that the following changes could fix the issue, right? > > If so, I will send a formal patch with your report and test, thanks. > > > Thanks for the quick response and apologies for the delay! > > Best, > > Gabe > > On Thu, Jul 21, 2022 at 9:57 PM Kefeng Wang <wangkefeng.wang@huawei.com> > wrote: > >> >> On 2022/7/21 23:58, Abhishek Shah wrote: >> >> Dear Kernel Maintainers, >> >> We found a race in mm/ksm.c. During the execution of the function >> *__ksm_run* which uses variable *ksm_run* to decide the list insertion >> point, the variable *ksm_run* can be concurrently modified in the >> function *run_store*, which we thought could be undesirable since “KSM >> pages in newly forked mms can be missed” (See comment here: >> https://elixir.bootlin.com/linux/v5.18-rc5/source/mm/ksm.c#L2498). We >> would also like your thoughts on the security impact given it is a TOCTOU >> bug. >> >> We provide more details below including the trace and reproducing >> test cases. >> >> >> Hello， could the following changes to avoid the data-race issue？ >> >> diff --git a/mm/ksm.c b/mm/ksm.c >> index 54f78c9eecae..f072753cbb3a 100644 >> --- a/mm/ksm.c >> +++ b/mm/ksm.c >> @@ -2497,6 +2497,7 @@ int __ksm_enter(struct mm_struct *mm) >> { >> struct mm_slot *mm_slot; >> int needs_wakeup; >> + bool ksm_run_merge; >> >> mm_slot = alloc_mm_slot(); >> if (!mm_slot) >> @@ -2505,6 +2506,10 @@ int __ksm_enter(struct mm_struct *mm) >> /* Check ksm_run too? Would need tighter locking */ >> needs_wakeup = list_empty(&ksm_mm_head.mm_list); >> >> + mutex_lock(&ksm_thread_mutex); >> + ksm_run_unmerge = !!(ksm_run & KSM_RUN_UNMERGE); >> + mutex_unlock(&ksm_thread_mutex); >> + >> spin_lock(&ksm_mmlist_lock); >> insert_to_mm_slots_hash(mm, mm_slot); >> /* >> @@ -2517,7 +2522,7 @@ int __ksm_enter(struct mm_struct *mm) >> * scanning cursor, otherwise KSM pages in newly forked mms will >> be >> * missed: then we might as well insert at the end of the list. >> */ >> - if (ksm_run & KSM_RUN_UNMERGE) >> + if (ksm_run_unmerge) >> list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list); >> else >> list_add_tail(&mm_slot->mm_list, >> &ksm_scan.mm_slot->mm_list); >> >> >> >> >> *Trace* >> BUG: KCSAN: data-race in __ksm_enter / run_store >> write to 0xffffffff881edae0 of 8 bytes by task 6542 on cpu 0: >> run_store+0x19a/0x2d0 mm/ksm.c:2897 >> kobj_attr_store+0x44/0x60 lib/kobject.c:824 >> sysfs_kf_write+0x16f/0x1a0 fs/sysfs/file.c:136 >> kernfs_fop_write_iter+0x2ae/0x370 fs/kernfs/file.c:291 >> call_write_iter include/linux/fs.h:2050 [inline] >> new_sync_write fs/read_write.c:504 [inline] >> vfs_write+0x779/0x900 fs/read_write.c:591 >> ksys_write+0xde/0x190 fs/read_write.c:644 >> __do_sys_write fs/read_write.c:656 [inline] >> __se_sys_write fs/read_write.c:653 [inline] >> __x64_sys_write+0x43/0x50 fs/read_write.c:653 >> do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 >> entry_SYSCALL_64_after_hwframe+0x44/0xae >> >> read to 0xffffffff881edae0 of 8 bytes by task 6541 on cpu 1: >> __ksm_enter+0x114/0x260 mm/ksm.c:2501 >> ksm_madvise+0x291/0x350 mm/ksm.c:2451 >> madvise_vma_behavior mm/madvise.c:1039 [inline] >> madvise_walk_vmas mm/madvise.c:1221 [inline] >> do_madvise+0x656/0xeb0 mm/madvise.c:1399 >> __do_sys_madvise mm/madvise.c:1412 [inline] >> __se_sys_madvise mm/madvise.c:1410 [inline] >> __x64_sys_madvise+0x64/0x70 mm/madvise.c:1410 >> do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 >> entry_SYSCALL_64_after_hwframe+0x44/0xae >> >> Reported by Kernel Concurrency Sanitizer on: >> CPU: 1 PID: 6541 Comm: syz-executor2-n Not tainted 5.18.0-rc5+ #107 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 >> 04/01/2014 >> --------------------- >> *Inputs * >> Input CPU 0: >> r0 = openat$sysctl(0xffffff9c, >> &(0x7f0000000100)='/sys/kernel/mm/ksm/run\x00', 0x1, 0x0) >> write$sysctl(r0, &(0x7f0000000000)='2\x00', 0x2) >> >> Input CPU 1: >> madvise(&(0x7f0000ffc000/0x4000)=nil, 0x4000, 0xc) >> mlock2(&(0x7f0000ffe000/0x2000)=nil, 0x2000, 0x0) >> madvise(&(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x12) >> clone(0x0, 0x0, 0x0, 0x0, 0x0) >> >> [-- Attachment #2: Type: text/html, Size: 9359 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-08-02 12:33 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-07-21 15:58 Race in mm/ksm.c Abhishek Shah 2022-07-22 1:57 ` Kefeng Wang 2022-08-02 11:44 ` Gabriel Ryan 2022-08-02 12:18 ` Kefeng Wang 2022-08-02 12:33 ` Gabriel Ryan
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