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[34.123.190.156]) by smtp.gmail.com with ESMTPSA id a16-20020a056638019000b0042af069eeefsm489720jaq.50.2023.08.31.10.18.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 31 Aug 2023 10:18:31 -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 , Matthew Wilcox , linux-mm@kvack.org Subject: [PATCH v2 1/2] mm/vmalloc: Add a safer version of find_vm_area() for debug Date: Thu, 31 Aug 2023 17:18:25 +0000 Message-ID: <20230831171827.2625016-1-joel@joelfernandes.org> X-Mailer: git-send-email 2.42.0.rc2.253.gd59a3bf2b4-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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(). [apply test robot feedback on unused function fix.] Reported-by: Zhen Lei Cc: Paul E. McKenney Cc: rcu@vger.kernel.org Cc: Zqiang Reviewed-by: Matthew Wilcox (Oracle) Signed-off-by: Joel Fernandes (Google) --- v1->v2: Apply review tags and test robot feedback. mm/vmalloc.c | 39 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 93cf99aba335..f09e882ae3b8 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1865,6 +1865,20 @@ struct vmap_area *find_vmap_area(unsigned long addr) return va; } +#ifdef CONFIG_PRINTK +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; +} +#endif + static struct vmap_area *find_unlink_vmap_area(unsigned long addr) { struct vmap_area *va; @@ -2671,6 +2685,29 @@ 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. + */ +#ifdef CONFIG_PRINTK +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; +} +#endif + /** * remove_vm_area - find and remove a continuous kernel virtual area * @addr: base address @@ -4277,7 +4314,7 @@ 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", -- 2.42.0.rc2.253.gd59a3bf2b4-goog