disallow seeks and appends on sysfs files - linux.kernel

Message from discussion disallow seeks and appends on sysfs files

Mitch Williams

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More options Jan 21 2005, 6:00 pm

Newsgroups: linux.kernel

From: Mitch Williams <mitch.a.willi...@intel.com>

Date: Sat, 22 Jan 2005 00:00:15 +0100

Local: Fri, Jan 21 2005 6:00 pm

Subject: [PATCH 1/3] disallow seeks and appends on sysfs files

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This patch causes sysfs to return errors if the caller attempts to append
to or seek on a sysfs file.

Generated from 2.6.11-rc1.

Signed-off-by: Mitch Williams <mitch.a.willi...@intel.com>

diff -uprN -X dontdiff linux-2.6.11-clean/fs/sysfs/file.c linux-2.6.11/fs/sysfs/file.c
--- linux-2.6.11-clean/fs/sysfs/file.c 2004-12-24 13:33:50.000000000 -0800
+++ linux-2.6.11/fs/sysfs/file.c 2005-01-21 13:09:21.000000000 -0800
@@ -281,6 +281,11 @@ static int check_perm(struct inode * ino
if (!ops)
goto Eaccess;

+ /* Is the file is open for append? Sorry, we don't do that. */
+ if (file->f_flags & O_APPEND) {
+ goto Einval;
+ }
+
/* File needs write support.
* The inode's perms must say it's ok,
* and we must have a store method.
@@ -312,6 +302,10 @@ static int check_perm(struct inode * ino
file->private_data = buffer;
} else
error = -ENOMEM;
+
+ /* Set mode bits to disallow seeking. */
+ file->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
+
goto Done;

Einval:
@@ -368,7 +343,7 @@ static int sysfs_release(struct inode *
struct file_operations sysfs_file_operations = {
.read = sysfs_read_file,
.write = sysfs_write_file,
- .llseek = generic_file_llseek,
+ .llseek = no_llseek,
.open = sysfs_open_file,
.release = sysfs_release,
};
-
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