| Message ID | 20231107213647.1405493-3-avadhut.naik@amd.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add support for Vendor Defined Error Types in Einj Module | expand |
> @@ -1042,7 +1060,7 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode, > struct dentry *parent, > struct debugfs_blob_wrapper *blob) > { > - return debugfs_create_file_unsafe(name, mode & 0444, parent, blob, &fops_blob); > + return debugfs_create_file_unsafe(name, mode, parent, blob, &fops_blob); > } The minimalist change here would be to s/0444/0666/ That would just allow callers to ask for writeable files without letting them add execute permission, or exotic modes like setuid etc. -Tony
Hi, On 11/7/2023 16:28, Luck, Tony wrote: >> @@ -1042,7 +1060,7 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode, >> struct dentry *parent, >> struct debugfs_blob_wrapper *blob) >> { >> - return debugfs_create_file_unsafe(name, mode & 0444, parent, blob, &fops_blob); >> + return debugfs_create_file_unsafe(name, mode, parent, blob, &fops_blob); >> } > > The minimalist change here would be to s/0444/0666/ > > That would just allow callers to ask for writeable files without letting them > add execute permission, or exotic modes like setuid etc. > Noted. Thanks for the clarification. Will change to something like below: return debugfs_create_file_unsafe(name, mode & 0666, parent, blob, &fops_blob); > -Tony
Hi Tony, On 11/7/2023 16:28, Luck, Tony wrote: >> @@ -1042,7 +1060,7 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode, >> struct dentry *parent, >> struct debugfs_blob_wrapper *blob) >> { >> - return debugfs_create_file_unsafe(name, mode & 0444, parent, blob, &fops_blob); >> + return debugfs_create_file_unsafe(name, mode, parent, blob, &fops_blob); >> } > > The minimalist change here would be to s/0444/0666/ > Just realized that s/0444/0644/ might be an even more minimalist change since you anyways, I think, need to be root for error injection through einj. Does that sound good? In any case, using 0666 will result in the below checkpatch warning: [root avadnaik-linux]# ./scripts/checkpatch.pl --strict -g HEAD WARNING: Exporting world writable files is usually an error. Consider more restrictive permissions. #84: FILE: fs/debugfs/file.c:1063: + return debugfs_create_file_unsafe(name, mode & 0666, parent, blob, &fops_blob); total: 0 errors, 1 warnings, 0 checks, 54 lines checked Would you be okay with s/0444/0644/? - return debugfs_create_file_unsafe(name, mode & 0444, parent, blob, &fops_blob); + return debugfs_create_file_unsafe(name, mode & 0644, parent, blob, &fops_blob); > That would just allow callers to ask for writeable files without letting them > add execute permission, or exotic modes like setuid etc. > > -Tony
> > The minimalist change here would be to s/0444/0666/ > > > Just realized that s/0444/0644/ might be an even more minimalist change since you anyways, > I think, need to be root for error injection through einj. Does that sound good? You need write access. I don't think you need to be root. E.g. a validation system might set up an "einj" group and "chmod" all these files to 0664. But that's nitpicking. > > In any case, using 0666 will result in the below checkpatch warning: > > [root avadnaik-linux]# ./scripts/checkpatch.pl --strict -g HEAD > WARNING: Exporting world writable files is usually an error. Consider more restrictive permissions. > #84: FILE: fs/debugfs/file.c:1063: > + return debugfs_create_file_unsafe(name, mode & 0666, parent, blob, &fops_blob); > > total: 0 errors, 1 warnings, 0 checks, 54 lines checked The warning is dubious. This code isn't necessarily exporting a world writeable file. But it does allow a caller of this routine to do that. > > Would you be okay with s/0444/0644/? > - return debugfs_create_file_unsafe(name, mode & 0444, parent, blob, &fops_blob); > + return debugfs_create_file_unsafe(name, mode & 0644, parent, blob, &fops_blob); Yes. This is fine (better). Make sure to mention in the commit comment that this allows callers to create files writeable by owner. -Tony
On 11/16/2023 12:44, Luck, Tony wrote: >>> The minimalist change here would be to s/0444/0666/ >>> >> Just realized that s/0444/0644/ might be an even more minimalist change since you anyways, >> I think, need to be root for error injection through einj. Does that sound good? > > You need write access. I don't think you need to be root. E.g. a validation system might > set up an "einj" group and "chmod" all these files to 0664. But that's nitpicking. > >> >> In any case, using 0666 will result in the below checkpatch warning: >> >> [root avadnaik-linux]# ./scripts/checkpatch.pl --strict -g HEAD >> WARNING: Exporting world writable files is usually an error. Consider more restrictive permissions. >> #84: FILE: fs/debugfs/file.c:1063: >> + return debugfs_create_file_unsafe(name, mode & 0666, parent, blob, &fops_blob); >> >> total: 0 errors, 1 warnings, 0 checks, 54 lines checked > > The warning is dubious. This code isn't necessarily exporting a world writeable file. But > it does allow a caller of this routine to do that. > >> >> Would you be okay with s/0444/0644/? > >> - return debugfs_create_file_unsafe(name, mode & 0444, parent, blob, &fops_blob); >> + return debugfs_create_file_unsafe(name, mode & 0644, parent, blob, &fops_blob); > > > Yes. This is fine (better). Make sure to mention in the commit comment that this allows > callers to create files writeable by owner. > Will do. Thanks for the confirmation! > -Tony > >
diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c index c45e8c2d62e1..dde1f5f30fb3 100644 --- a/fs/debugfs/file.c +++ b/fs/debugfs/file.c @@ -1008,17 +1008,35 @@ static ssize_t read_file_blob(struct file *file, char __user *user_buf, return r; } +static ssize_t write_file_blob(struct file *file, const char __user *user_buf, + size_t count, loff_t *ppos) +{ + struct debugfs_blob_wrapper *blob = file->private_data; + struct dentry *dentry = F_DENTRY(file); + ssize_t r; + + r = debugfs_file_get(dentry); + if (unlikely(r)) + return r; + r = simple_write_to_buffer(blob->data, blob->size, ppos, user_buf, + count); + + debugfs_file_put(dentry); + return r; +} + static const struct file_operations fops_blob = { .read = read_file_blob, + .write = write_file_blob, .open = simple_open, .llseek = default_llseek, }; /** - * debugfs_create_blob - create a debugfs file that is used to read a binary blob + * debugfs_create_blob - create a debugfs file that is used to read and write + * a binary blob * @name: a pointer to a string containing the name of the file to create. - * @mode: the read permission that the file should have (other permissions are - * masked out) + * @mode: the permission that the file should have * @parent: a pointer to the parent dentry for this file. This should be a * directory dentry if set. If this parameter is %NULL, then the * file will be created in the root of the debugfs filesystem. @@ -1027,7 +1045,7 @@ static const struct file_operations fops_blob = { * * This function creates a file in debugfs with the given name that exports * @blob->data as a binary blob. If the @mode variable is so set it can be - * read from. Writing is not supported. + * read from and written to. * * This function will return a pointer to a dentry if it succeeds. This * pointer must be passed to the debugfs_remove() function when the file is @@ -1042,7 +1060,7 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode, struct dentry *parent, struct debugfs_blob_wrapper *blob) { - return debugfs_create_file_unsafe(name, mode & 0444, parent, blob, &fops_blob); + return debugfs_create_file_unsafe(name, mode, parent, blob, &fops_blob); } EXPORT_SYMBOL_GPL(debugfs_create_blob);