debugfs: fix error when writing negative value to atomic_t debugfs file

[ Upstream commit d472cf797c4e268613dbce5ec9b95d0bcae19ecb ]

The simple attribute files do not accept a negative value since the commit
488dac0c9237 ("libfs: fix error cast of negative value in
simple_attr_write()"), so we have to use a 64-bit value to write a
negative value for a debugfs file created by debugfs_create_atomic_t().

This restores the previous behaviour by introducing
DEFINE_DEBUGFS_ATTRIBUTE_SIGNED for a signed value.

Link: https://lkml.kernel.org/r/20220919172418.45257-4-akinobu.mita@gmail.com
Fixes: 488dac0c9237 ("libfs: fix error cast of negative value in simple_attr_write()")
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Reported-by: Zhao Gongyi <zhaogongyi@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Wei Yongjun <weiyongjun1@huawei.com>
Cc: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/Documentation/fault-injection/fault-injection.rst b/Documentation/fault-injection/fault-injection.rst
index 4a25c5e..8c47847 100644 (file)
--- a/Documentation/fault-injection/fault-injection.rst
+++ b/Documentation/fault-injection/fault-injection.rst
@@ -83,9 +83,7 @@ configuration of fault-injection capabilities.
 - /sys/kernel/debug/fail*/times:
 
        specifies how many times failures may happen at most. A value of -1
-       means "no limit". Note, though, that this file only accepts unsigned
-       values. So, if you want to specify -1, you better use 'printf' instead
-       of 'echo', e.g.: $ printf %#x -1 > times
+       means "no limit".
 
 - /sys/kernel/debug/fail*/space:
 
@@ -277,7 +275,7 @@ Application Examples
     echo Y > /sys/kernel/debug/$FAILTYPE/task-filter
     echo 10 > /sys/kernel/debug/$FAILTYPE/probability
     echo 100 > /sys/kernel/debug/$FAILTYPE/interval
-    printf %#x -1 > /sys/kernel/debug/$FAILTYPE/times
+    echo -1 > /sys/kernel/debug/$FAILTYPE/times
     echo 0 > /sys/kernel/debug/$FAILTYPE/space
     echo 2 > /sys/kernel/debug/$FAILTYPE/verbose
     echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
@@ -331,7 +329,7 @@ Application Examples
     echo N > /sys/kernel/debug/$FAILTYPE/task-filter
     echo 10 > /sys/kernel/debug/$FAILTYPE/probability
     echo 100 > /sys/kernel/debug/$FAILTYPE/interval
-    printf %#x -1 > /sys/kernel/debug/$FAILTYPE/times
+    echo -1 > /sys/kernel/debug/$FAILTYPE/times
     echo 0 > /sys/kernel/debug/$FAILTYPE/space
     echo 2 > /sys/kernel/debug/$FAILTYPE/verbose
     echo 1 > /sys/kernel/debug/$FAILTYPE/ignore-gfp-wait
@@ -362,7 +360,7 @@ Application Examples
     echo N > /sys/kernel/debug/$FAILTYPE/task-filter
     echo 100 > /sys/kernel/debug/$FAILTYPE/probability
     echo 0 > /sys/kernel/debug/$FAILTYPE/interval
-    printf %#x -1 > /sys/kernel/debug/$FAILTYPE/times
+    echo -1 > /sys/kernel/debug/$FAILTYPE/times
     echo 0 > /sys/kernel/debug/$FAILTYPE/space
     echo 1 > /sys/kernel/debug/$FAILTYPE/verbose
 

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 950c63f..38930d9 100644 (file)
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -378,8 +378,8 @@ ssize_t debugfs_attr_read(struct file *file, char __user *buf,
 }
 EXPORT_SYMBOL_GPL(debugfs_attr_read);
 
-ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
-                        size_t len, loff_t *ppos)
+static ssize_t debugfs_attr_write_xsigned(struct file *file, const char __user *buf,
+                        size_t len, loff_t *ppos, bool is_signed)
 {
        struct dentry *dentry = F_DENTRY(file);
        ssize_t ret;
@@ -387,12 +387,28 @@ ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
        ret = debugfs_file_get(dentry);
        if (unlikely(ret))
                return ret;
-       ret = simple_attr_write(file, buf, len, ppos);
+       if (is_signed)
+               ret = simple_attr_write_signed(file, buf, len, ppos);
+       else
+               ret = simple_attr_write(file, buf, len, ppos);
        debugfs_file_put(dentry);
        return ret;
 }
+
+ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
+                        size_t len, loff_t *ppos)
+{
+       return debugfs_attr_write_xsigned(file, buf, len, ppos, false);
+}
 EXPORT_SYMBOL_GPL(debugfs_attr_write);
 
+ssize_t debugfs_attr_write_signed(struct file *file, const char __user *buf,
+                        size_t len, loff_t *ppos)
+{
+       return debugfs_attr_write_xsigned(file, buf, len, ppos, true);
+}
+EXPORT_SYMBOL_GPL(debugfs_attr_write_signed);
+
 static struct dentry *debugfs_create_mode_unsafe(const char *name, umode_t mode,
                                        struct dentry *parent, void *value,
                                        const struct file_operations *fops,
@@ -738,11 +754,11 @@ static int debugfs_atomic_t_get(void *data, u64 *val)
        *val = atomic_read((atomic_t *)data);
        return 0;
 }
-DEFINE_DEBUGFS_ATTRIBUTE(fops_atomic_t, debugfs_atomic_t_get,
+DEFINE_DEBUGFS_ATTRIBUTE_SIGNED(fops_atomic_t, debugfs_atomic_t_get,
                        debugfs_atomic_t_set, "%lld\n");
-DEFINE_DEBUGFS_ATTRIBUTE(fops_atomic_t_ro, debugfs_atomic_t_get, NULL,
+DEFINE_DEBUGFS_ATTRIBUTE_SIGNED(fops_atomic_t_ro, debugfs_atomic_t_get, NULL,
                        "%lld\n");
-DEFINE_DEBUGFS_ATTRIBUTE(fops_atomic_t_wo, NULL, debugfs_atomic_t_set,
+DEFINE_DEBUGFS_ATTRIBUTE_SIGNED(fops_atomic_t_wo, NULL, debugfs_atomic_t_set,
                        "%lld\n");
 
 /**

diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
index f606746..ea2d919 100644 (file)
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -45,7 +45,7 @@ struct debugfs_u32_array {
 
 extern struct dentry *arch_debugfs_dir;
 
-#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt)          \
+#define DEFINE_DEBUGFS_ATTRIBUTE_XSIGNED(__fops, __get, __set, __fmt, __is_signed)     \
 static int __fops ## _open(struct inode *inode, struct file *file)     \
 {                                                                      \
        __simple_attr_check_format(__fmt, 0ull);                        \
@@ -56,10 +56,16 @@ static const struct file_operations __fops = {                              \
        .open    = __fops ## _open,                                     \
        .release = simple_attr_release,                                 \
        .read    = debugfs_attr_read,                                   \
-       .write   = debugfs_attr_write,                                  \
+       .write   = (__is_signed) ? debugfs_attr_write_signed : debugfs_attr_write,      \
        .llseek  = no_llseek,                                           \
 }
 
+#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt)          \
+       DEFINE_DEBUGFS_ATTRIBUTE_XSIGNED(__fops, __get, __set, __fmt, false)
+
+#define DEFINE_DEBUGFS_ATTRIBUTE_SIGNED(__fops, __get, __set, __fmt)   \
+       DEFINE_DEBUGFS_ATTRIBUTE_XSIGNED(__fops, __get, __set, __fmt, true)
+
 typedef struct vfsmount *(*debugfs_automount_t)(struct dentry *, void *);
 
 #if defined(CONFIG_DEBUG_FS)
@@ -102,6 +108,8 @@ ssize_t debugfs_attr_read(struct file *file, char __user *buf,
                        size_t len, loff_t *ppos);
 ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
                        size_t len, loff_t *ppos);
+ssize_t debugfs_attr_write_signed(struct file *file, const char __user *buf,
+                       size_t len, loff_t *ppos);
 
 struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
                 struct dentry *new_dir, const char *new_name);
@@ -254,6 +262,13 @@ static inline ssize_t debugfs_attr_write(struct file *file,
        return -ENODEV;
 }
 
+static inline ssize_t debugfs_attr_write_signed(struct file *file,
+                                       const char __user *buf,
+                                       size_t len, loff_t *ppos)
+{
+       return -ENODEV;
+}
+
 static inline struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
                 struct dentry *new_dir, char *new_name)
 {