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[34.123.190.156]) by smtp.gmail.com with ESMTPSA id k8-20020a926f08000000b00348880831fdsm3701371ilc.58.2023.08.30.04.04.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Aug 2023 04:04:07 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org, Andrew Morton , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes Cc: "Joel Fernandes (Google)" , Zhen Lei , "Paul E . McKenney" , rcu@vger.kernel.org, Zqiang , linux-mm@kvack.org Subject: [PATCH 1/2] mm/vmalloc: Add a safer version of find_vm_area() for debug Date: Wed, 30 Aug 2023 11:03:59 +0000 Message-ID: <20230830110402.386898-1-joel@joelfernandes.org> X-Mailer: git-send-email 2.42.0.rc2.253.gd59a3bf2b4-goog MIME-Version: 1.0 X-Rspamd-Queue-Id: 92D7F40006 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: pkhjpcsgzmgrjfqhe36cgec9ys7htfcj X-HE-Tag: 1693393448-555832 X-HE-Meta: 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 I3UZzEiS 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 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: It is unsafe to dump vmalloc area information when trying to do so from some contexts. Add a safer trylock version of the same function to do a best-effort VMA finding and use it from vmalloc_dump_obj(). Reported-by: Zhen Lei Cc: Paul E. McKenney Cc: rcu@vger.kernel.org Cc: Zqiang Signed-off-by: Joel Fernandes (Google) Reviewed-by: Matthew Wilcox (Oracle) --- mm/vmalloc.c | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 93cf99aba335..dae347e446e6 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1865,6 +1865,18 @@ struct vmap_area *find_vmap_area(unsigned long addr) return va; } +static struct vmap_area *find_vmap_area_trylock(unsigned long addr) +{ + struct vmap_area *va; + + if (!spin_trylock(&vmap_area_lock)) + return NULL; + va = __find_vmap_area(addr, &vmap_area_root); + spin_unlock(&vmap_area_lock); + + return va; +} + static struct vmap_area *find_unlink_vmap_area(unsigned long addr) { struct vmap_area *va; @@ -2671,6 +2683,27 @@ struct vm_struct *find_vm_area(const void *addr) return va->vm; } +/** + * try_to_find_vm_area - find a continuous kernel virtual area + * @addr: base address + * + * This function is the same as find_vm_area() except that it is + * safe to call if vmap_area_lock is already held and returns NULL + * if it is. See comments in find_vmap_area() for other details. + * + * Return: the area descriptor on success or %NULL on failure. + */ +static struct vm_struct *try_to_find_vm_area(const void *addr) +{ + struct vmap_area *va; + + va = find_vmap_area_trylock((unsigned long)addr); + if (!va) + return NULL; + + return va->vm; +} + /** * remove_vm_area - find and remove a continuous kernel virtual area * @addr: base address @@ -4277,7 +4310,7 @@ bool vmalloc_dump_obj(void *object) struct vm_struct *vm; void *objp = (void *)PAGE_ALIGN((unsigned long)object); - vm = find_vm_area(objp); + vm = try_to_find_vm_area(objp); if (!vm) return false; pr_cont(" %u-page vmalloc region starting at %#lx allocated at %pS\n",