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McKenney" , Petr Mladek , Kees Cook , David Disseldorp Subject: [PATCH 5/7] misc: reject duplicate names in misc_register() Date: Thu, 14 May 2026 05:04:53 +0000 Message-Id: <20260514050455.2954509-6-justin.he@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260514050455.2954509-1-justin.he@arm.com> References: <20260514050455.2954509-1-justin.he@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 2E5CDA0007 X-Rspam-User: X-Stat-Signature: mktyixuk81cdo1d83getrwugsgibxjoe X-HE-Tag: 1778735270-330531 X-HE-Meta: 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 DhHGyDw7 0Mgl/gRpYdURU1W8SPqvGenXkztZiHPtNmFvMinzbmphp+oy9XT/iX0CrN/yRVatLe+D0NJVUgOAYBuU1N4/caR0W1T8ombOYjPTb6HWGlbVb2zhgjpDupg3LJdzrGeRlTQItnjHb8dWzLh7Dfk+J4e1MPxhaYoldomuuYwFirw2DjIZ8/Ry7mJQ5XCOkSFqz4aISGrF5BEH87jvruHOzuZuunyHqbxlZR5d9sFeY4ZvuJiKabODPtMiq3RSxSrREt2cZzVy+0EWt6Ej6CD3ocWuSvtr3UYFEbLl7dcD2nVDMcDnSMox/qlV9qoSF+xRYCrHNNFyrJbMiFdSxi+81QY1NofghwZnyYlvQ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The miscdev kunit suite registers two miscdevices with the same name and expects -EEXIST. The second call currently goes all the way to sysfs_create_dir_ns(), which prints "cannot create duplicate filename" with a backtrace on every run. Walk misc_list under misc_mtx, return -EEXIST on a name collision and free the just-allocated minor before returning. To: Arnd Bergmann To: Greg Kroah-Hartman Signed-off-by: Jia He --- drivers/char/misc.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/drivers/char/misc.c b/drivers/char/misc.c index 726516fb0a3b..d6ffa21ac495 100644 --- a/drivers/char/misc.c +++ b/drivers/char/misc.c @@ -248,6 +248,28 @@ int misc_register(struct miscdevice *misc) } } + /* + * Detect duplicate names up-front so the subsequent + * device_create_with_groups() does not trip + * sysfs_create_dir_ns()->sysfs_warn_dup(), which unconditionally + * dumps a stack trace. Both the existing miscdev kunit suite + * (miscdev_test_duplicate_name) and any caller racing on the same + * name would otherwise pollute dmesg on every -EEXIST. + */ + { + struct miscdevice *c; + + list_for_each_entry(c, &misc_list, list) { + if (strcmp(c->name, misc->name) == 0) { + misc_minor_free(misc->minor); + if (is_dynamic) + misc->minor = MISC_DYNAMIC_MINOR; + err = -EEXIST; + goto out; + } + } + } + dev = MKDEV(MISC_MAJOR, misc->minor); misc->this_device = -- 2.34.1