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Wed, 07 May 2025 06:07:19 -0700 (PDT) MIME-Version: 1.0 References: <20250506082520.84153-1-aha310510@gmail.com> In-Reply-To: From: Jeongjun Park Date: Wed, 7 May 2025 22:07:08 +0900 X-Gm-Features: ATxdqUEjuEtyhw43XJqZk91crVOvGCzd78Ivgf5Vy1ExAzawMOZpQI7L5pXs9xM Message-ID: Subject: Re: [PATCH v2] mm/vmalloc: fix data race in show_numa_info() To: Uladzislau Rezki Cc: akpm@linux-foundation.org, edumazet@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: D5F2C140012 X-Stat-Signature: st9y6wii4aapcuuq4y6moresgnijkxa6 X-Rspam-User: X-HE-Tag: 1746623240-342699 X-HE-Meta: U2FsdGVkX1/9eGGBBz75pyftommn6F90cTXhSKBB1DlcyAtWRvHuBLu1zhNkvPV91lCTHnPnEOjek5Eq9/GscBRKdZsPWKa5TLoO2uxkJBI5Y0LrgPFJKibny1JGdpUadw8Zq4fDhm/ZmkyOJqJGWsvmdymu+aXQRfQ4ViAjTimW3EDMbnV0gEc8mkbOegKilQg2xbk6sOifyQjtIwLg8unjoeg7KFeWwC6W/7/NQKdhsUpgSpiZUTrt2BlHCkNmwE02hrhHySGNhFcQCDZGEtHPf9AMAj2D/jdAwrZ/+Ra+symzQhF9ffGSvmOlKftnH1Wc8uuf55t7IhL/mjMpF68/6OdzVCXYokBemFiPsi1wpD/lytn3OOum8QeT8VVZiSamrbbwW4k8yxNCGUR9g1WUQueMyGAE1taeM2mUK478Y4KYhoneDxAuxJLOqPgLCex9KtjAWAEkRXiZzIPGStRBszN+arrd6DBw8jfPE+03a18tWvIuED1+NYMcKuult24EFfoM6XrTVZrzrLqXgF346GcngppUjbz3IMpbFa0Mv2xwSJDhrKs0Yh5CyePLv886jh3W/HDvlnkbDc/s9N7bXudmlVyDDQ5ythqaX6ppYnZIX6O8qzedlEkALzbtR9XdPYptohzozjllSwiGFLyKP1ngQwT1vpdC8eNqhRzY8fPMVDPA3HQwcUSo4JxyN9mLrQG1xPoxRS5vhKF8mfJT06Q1K8L1AOvUX9J4DfCDZ87WtCEdSqjIzCQ4dpaB+Ets5Au5c7kJJEsYHCH8AkUvrHwZ288HJNKec0MrnSC0B0RGfo9+cVhSZPYigAEVH5QLTH8Uls1aXqImHC3Hd14tr/RLAgeRc0wVkkLOoDAUo2KIRpcvC9cG2C6tb1JH9PQHsLKlsNd+7lPLoZVykZ07tJcofhr7F4gy95baJrl0+kOtuvW5AZD3CAjDQepkodIdrshV42lk+hfYv4d FECPkTNH MVMoe89XMxK3Qm08yFpiFUqFYsW16g1CQ+EYLvIOCRLrmAME13Uw4vKSwNZRwy/Dg37T9PprGvrNQ3jV/MldTqGWuB7SrPx97mT91wALMwNpQ4dkrV4dCDJFRIB+UpIkw9q0xwLGsN6qZCu4izAP3Fmj/w6363UZqsERo7uHd5V9z1zPY8zwlyhzxbh7FmuvxQ5DBdFlsdOgSW39Sicmr+7Zkh6bOEmTWv8i+v3E4cVK7s0pf20cPrEa+aKZ4PtKAjGQ8f3w1BWb6vkpisGSPlPq4mUR1ppsgVOA13hBeq4p8qvNlOIC/z6gOSeyKUp3XTtFmgIzOOSBbcgs9nm4m6JiEUM6Ltp+amCm4j3cF5E8iOqS46jBzHNAB+aqWekrA6KhKQMZVo4USyGCFzpv/ZhJecizg0TQ1z7mfc/vc2ayN0aIHaMyjUHGC9Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Uladzislau Rezki wrote: > > On Tue, May 06, 2025 at 05:25:19PM +0900, Jeongjun Park wrote: > > The following data-race was found in show_numa_info(): > > > > ================================================================== > > BUG: KCSAN: data-race in vmalloc_info_show / vmalloc_info_show > > > > read to 0xffff88800971fe30 of 4 bytes by task 8289 on cpu 0: > > show_numa_info mm/vmalloc.c:4936 [inline] > > vmalloc_info_show+0x5a8/0x7e0 mm/vmalloc.c:5016 > > seq_read_iter+0x373/0xb40 fs/seq_file.c:230 > > proc_reg_read_iter+0x11e/0x170 fs/proc/inode.c:299 > > new_sync_read fs/read_write.c:489 [inline] > > vfs_read+0x5b4/0x740 fs/read_write.c:570 > > ksys_read+0xbe/0x190 fs/read_write.c:713 > > __do_sys_read fs/read_write.c:722 [inline] > > __se_sys_read fs/read_write.c:720 [inline] > > __x64_sys_read+0x41/0x50 fs/read_write.c:720 > > x64_sys_call+0x1729/0x1fd0 arch/x86/include/generated/asm/syscalls_64.h:1 > > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > > do_syscall_64+0xa6/0x1b0 arch/x86/entry/syscall_64.c:94 > > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > > > write to 0xffff88800971fe30 of 4 bytes by task 8287 on cpu 1: > > show_numa_info mm/vmalloc.c:4934 [inline] > > vmalloc_info_show+0x38f/0x7e0 mm/vmalloc.c:5016 > > seq_read_iter+0x373/0xb40 fs/seq_file.c:230 > > proc_reg_read_iter+0x11e/0x170 fs/proc/inode.c:299 > > new_sync_read fs/read_write.c:489 [inline] > > vfs_read+0x5b4/0x740 fs/read_write.c:570 > > ksys_read+0xbe/0x190 fs/read_write.c:713 > > __do_sys_read fs/read_write.c:722 [inline] > > __se_sys_read fs/read_write.c:720 [inline] > > __x64_sys_read+0x41/0x50 fs/read_write.c:720 > > x64_sys_call+0x1729/0x1fd0 arch/x86/include/generated/asm/syscalls_64.h:1 > > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > > do_syscall_64+0xa6/0x1b0 arch/x86/entry/syscall_64.c:94 > > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > > > value changed: 0x0000008f -> 0x00000000 > > ================================================================== > > > > According to this report, there is a read/write data-race because m->private > > is accessible to multiple CPUs. To fix this, instead of allocating the heap > > in proc_vmalloc_init() and passing the heap address to m->private, > > show_numa_info() should allocate the heap. > > > > One thing to note is that show_numa_info() is called in a critical section > > of a spinlock, so it must be allocated on the heap with GFP_ATOMIC flag. > > > > Fixes: a47a126ad5ea ("vmallocinfo: add NUMA information") > > Suggested-by: Eric Dumazet > > Signed-off-by: Jeongjun Park > > --- > > v2: Refactoring some functions and fix patch as per Eric Dumazet suggestion > > - Link to v1: https://lore.kernel.org/all/20250505171948.24410-1-aha310510@gmail.com/ > > --- > > mm/vmalloc.c | 50 +++++++++++++++++++++++++------------------------- > > 1 file changed, 25 insertions(+), 25 deletions(-) > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index 3ed720a787ec..a5e795346141 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -4914,28 +4914,32 @@ bool vmalloc_dump_obj(void *object) > > #endif > > > > #ifdef CONFIG_PROC_FS > > + > > +/* > > + * Print number of pages allocated on each memory node. > > + * > > + * This function can only be called if CONFIG_NUMA is enabled > > + * and VM_UNINITIALIZED bit in v->flags is disabled. > > + */ > > static void show_numa_info(struct seq_file *m, struct vm_struct *v) > > { > > - if (IS_ENABLED(CONFIG_NUMA)) { > > - unsigned int nr, *counters = m->private; > > - unsigned int step = 1U << vm_area_page_order(v); > > + unsigned int nr, *counters; > > + unsigned int step = 1U << vm_area_page_order(v); > > > > - if (!counters) > > - return; > > + counters = kcalloc(nr_node_ids, sizeof(unsigned int), GFP_ATOMIC); > > + if (!counters) > > + return; > > > > - if (v->flags & VM_UNINITIALIZED) > > - return; > > - /* Pair with smp_wmb() in clear_vm_uninitialized_flag() */ > > - smp_rmb(); > > + /* Pair with smp_wmb() in clear_vm_uninitialized_flag() */ > > + smp_rmb(); > > > > - memset(counters, 0, nr_node_ids * sizeof(unsigned int)); > > + for (nr = 0; nr < v->nr_pages; nr += step) > > + counters[page_to_nid(v->pages[nr])] += step; > > + for_each_node_state(nr, N_HIGH_MEMORY) > > + if (counters[nr]) > > + seq_printf(m, " N%u=%u", nr, counters[nr]); > > > > - for (nr = 0; nr < v->nr_pages; nr += step) > > - counters[page_to_nid(v->pages[nr])] += step; > > - for_each_node_state(nr, N_HIGH_MEMORY) > > - if (counters[nr]) > > - seq_printf(m, " N%u=%u", nr, counters[nr]); > > - } > > + kfree(counters); > > } > > > > static void show_purge_info(struct seq_file *m) > > @@ -5013,7 +5017,10 @@ static int vmalloc_info_show(struct seq_file *m, void *p) > > if (is_vmalloc_addr(v->pages)) > > seq_puts(m, " vpages"); > > > > - show_numa_info(m, v); > > + if (!(v->flags & VM_UNINITIALIZED) && > > > I think it makes sense to move the VM_UNINITIALIZED check before: > > > v = va->vm; > > seq_printf(m, "0x%pK-0x%pK %7ld", > v->addr, v->addr + v->size, v->size); > > > because it can be still un-initialized, thus flags like "nr_pages", etc > will not be valid. > > Any thoughts? It has nothing to do with a patch, because it fixes other > race issue and what i propose might well be a separate patch if we agree. > > Thanks! > > -- > Uladzislau Rezki That's absolutely correct. If the VM_UNINITIALIZED bit is enabled, it means there are uninitialized member variables, so printing the vm_struct information is not very appropriate. I think it would be better to add the VM_UNINITIALIZED bit check code right after `v = va->vm;`. This change isn't that complicated, so I'll add it to the v3 patch and send it. Regards, Jeongjun Park