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char: misc: Does not request module for miscdevice with dynamic minor

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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.qualcomm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Zijun Hu
2025-07-14 23:34:17 +08:00
committed by Greg Kroah-Hartman
parent 52e2bb5ff0
commit 1ba0fb42aa
1 changed files with 5 additions and 3 deletions
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8
drivers/char/misc.c
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@@ -132,7 +132,8 @@ static int misc_open(struct inode *inode, struct file *file)
break; break;
} }
if (!new_fops) { /* Only request module for fixed minor code */
if (!new_fops && minor < MISC_DYNAMIC_MINOR) {
mutex_unlock(&misc_mtx); mutex_unlock(&misc_mtx);
request_module("char-major-%d-%d", MISC_MAJOR, minor); request_module("char-major-%d-%d", MISC_MAJOR, minor);
mutex_lock(&misc_mtx); mutex_lock(&misc_mtx);
@@ -144,10 +145,11 @@ static int misc_open(struct inode *inode, struct file *file)
new_fops = fops_get(iter->fops); new_fops = fops_get(iter->fops);
break; break;
} }
if (!new_fops)
goto fail;
} }
if (!new_fops)
goto fail;
/* /*
* Place the miscdevice in the file's * Place the miscdevice in the file's
* private_data so it can be used by the * private_data so it can be used by the