5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Zijun Hu zijun.hu@oss.qualcomm.com
[ Upstream commit 1ba0fb42aa6a5f072b1b8c0b0520b32ad4ef4b45 ]
misc_open() may request module for miscdevice with dynamic minor, which is meaningless since:
- The dynamic minor allocated is unknown in advance without registering miscdevice firstly. - Macro MODULE_ALIAS_MISCDEV() is not applicable for dynamic minor.
Fix by only requesting module for miscdevice with fixed minor.
Acked-by: Thadeu Lima de Souza Cascardo cascardo@igalia.com Signed-off-by: Zijun Hu zijun.hu@oss.qualcomm.com Link: https://lore.kernel.org/r/20250714-rfc_miscdev-v6-6-2ed949665bde@oss.qualcom... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/char/misc.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/char/misc.c b/drivers/char/misc.c index f6a147427029a..cbe86a1f2244b 100644 --- a/drivers/char/misc.c +++ b/drivers/char/misc.c @@ -113,7 +113,8 @@ static int misc_open(struct inode *inode, struct file *file) } }
- if (!new_fops) { + /* Only request module for fixed minor code */ + if (!new_fops && minor < MISC_DYNAMIC_MINOR) { mutex_unlock(&misc_mtx); request_module("char-major-%d-%d", MISC_MAJOR, minor); mutex_lock(&misc_mtx); @@ -124,10 +125,11 @@ static int misc_open(struct inode *inode, struct file *file) break; } } - if (!new_fops) - goto fail; }
+ if (!new_fops) + goto fail; + /* * Place the miscdevice in the file's * private_data so it can be used by the