Ok. I will update the code example and come back later with some answers. On Fri, Apr 1, 2022, 5:32 PM Xiang Xiao <[email protected]> wrote:
> We need to try some ioctl with read/write some driver(e.g. serial driver > baud) internal state. > > > On Fri, Apr 1, 2022 at 10:05 PM Petro Karashchenko < > [email protected]> wrote: > > > Hello, > > > > Here I'm talking not about driver registration permission, but more about > > the "oflag" parameter to "open()" call. > > > > I just tried a quick example on MAC > > > > #include <fcntl.h> > > #include <stdio.h> > > > > int main(void) > > { > > int fd = open("test.txt", 0); > > if (fd < 0) > > printf("A\n"); > > else > > printf("B\n"); > > > > return 0; > > } > > > > The "B" is printed if the file exists. If you know the system that will > run > > this sample code and will print "A", please let me know. > > > > Best regards, > > Petro > > > > пт, 1 квіт. 2022 р. о 16:27 Alan Carvalho de Assis <[email protected]> > > пише: > > > > > I think the device file shouldn't be created with permission 000. > > > > > > Look inside your Linux /dev all device files have RW permission for > > > root, some give only R for group and others. > > > > > > So, probably we need to fix the device register creation, not removing > > > the flag check. > > > > > > BR, > > > > > > Alan > > > > > > On 4/1/22, Xiang Xiao <[email protected]> wrote: > > > > It's better to check ioctl callback too since ioctl means the driver > > has > > > > the compatibility of read(i)and write(o). > > > > > > > > On Fri, Apr 1, 2022 at 9:15 PM Petro Karashchenko < > > > > [email protected]> wrote: > > > > > > > >> So Alan do you suggest to remove inode_checkflags? > > > >> > > > >> On Fri, Apr 1, 2022, 4:13 PM Alan Carvalho de Assis < > > [email protected]> > > > >> wrote: > > > >> > > > >> > Hi Petro, > > > >> > > > > >> > I saw your PR #1117 but I think opening a device file with flag 0 > is > > > >> > not correct, please see the open man-pages: > > > >> > > > > >> > alan@dev:/tmp$ man 2 open > > > >> > > > > >> > The argument flags must include one of the following > access > > > >> > modes: O_RDONLY, O_WRONLY, or > > > >> > O_RDWR. These request opening the file read-only, > > write-only, > > > >> > or read/write, respectively. > > > >> > > > > >> > Also the opengroup say something similar: > > > >> > > > > >> > > > https://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html > > > >> > > > > >> > "Values for oflag are constructed by a bitwise-inclusive OR of > flags > > > >> > from the following list, defined in <fcntl.h>. Applications shall > > > >> > specify exactly one of the first five values (file access modes) > > below > > > >> > in the value of oflag:" > > > >> > > > > >> > The man pages uses "MUST", the OpenGroups uses "SHALL", but > > according > > > >> > to RFC2119 they are equivalents: > > > >> > > > > >> > https://www.ietf.org/rfc/rfc2119.txt > > > >> > > > > >> > BR, > > > >> > > > > >> > Alan > > > >> > > > > >> > On 4/1/22, Petro Karashchenko <[email protected]> > wrote: > > > >> > > Hi, > > > >> > > > > > >> > > I want to resume this thread again because after reexamined code > > > >> > carefully > > > >> > > I found that VFS layer has an API > > > >> > > > > > >> > > int inode_checkflags(FAR struct inode *inode, int oflags) > > > >> > > { > > > >> > > if (((oflags & O_RDOK) != 0 && !inode->u.i_ops->read) || > > > >> > > ((oflags & O_WROK) != 0 && !inode->u.i_ops->write)) > > > >> > > { > > > >> > > return -EACCES; > > > >> > > } > > > >> > > else > > > >> > > { > > > >> > > return OK; > > > >> > > } > > > >> > > } > > > >> > > > > > >> > > That checks if read and write handlers are available, so all our > > > >> > discussion > > > >> > > about R/W mode for IOCTL does not make any sense. We either need > > to > > > >> > remove > > > >> > > this check or register VFS nodes with proper permissions and > open > > > >> > > files > > > >> > > with correct flags. So if the driver does not have neither read > > nor > > > >> write > > > >> > > handlers the "0000" mode should be used and "0" should be used > > > during > > > >> > > opening of a file. Or we need to remove "inode_checkflags()". > > > >> > > > > > >> > > Best regards, > > > >> > > Petro > > > >> > > > > > >> > > пт, 28 січ. 2022 р. о 15:11 Petro Karashchenko > > > >> > > <[email protected]> > > > >> > > пише: > > > >> > > > > > >> > >> I see. Thank you for the feedback. I will rework changes to get > > > back > > > >> > >> read permissions. > > > >> > >> > > > >> > >> Best regards, > > > >> > >> Petro > > > >> > >> > > > >> > >> пт, 28 січ. 2022 р. о 14:41 Alan Carvalho de Assis > > > >> > >> <[email protected] > > > >> > > > > >> > >> пише: > > > >> > >> > > > > >> > >> > Hi Petro, > > > >> > >> > > > > >> > >> > The read permission is needed even when you just want to > open a > > > >> file: > > > >> > >> > > > > >> > >> > $ vim noreadfile > > > >> > >> > > > > >> > >> > $ chmod 0000 noreadfile > > > >> > >> > > > > >> > >> > $ ls -l noreadfile > > > >> > >> > ---------- 1 user user 5 jan 28 09:24 noreadfile > > > >> > >> > > > > >> > >> > $ cat noreadfile > > > >> > >> > cat: noreadfile: Permission denied > > > >> > >> > > > > >> > >> > You can even try to create a C program just to open it, and > it > > > >> > >> > will > > > >> > >> > fail. > > > >> > >> > > > > >> > >> > See the man page of open function: > > > >> > >> > > > > >> > >> > The argument flags *must* include one of the > following > > > >> access > > > >> > >> > modes: O_RDONLY, O_WRONLY, or > > > >> > >> > O_RDWR. These request opening the file read-only, > > > >> write-only, > > > >> > >> > or read/write, respectively. > > > >> > >> > > > > >> > >> > This man page makes it clear you must include an access mode, > > but > > > >> > >> > I > > > >> > >> > passed 0 to the access mode flag of open() and it was > accepted, > > > >> > >> > but > > > >> > >> > when the file has permission 0000 it returns -EPERM: "Failed > to > > > >> > >> > open > > > >> > >> > file: error -1" > > > >> > >> > > > > >> > >> > BR, > > > >> > >> > > > > >> > >> > Alan > > > >> > >> > > > > >> > >> > On 1/28/22, Petro Karashchenko <[email protected] > > > > > >> wrote: > > > >> > >> > > Hello, > > > >> > >> > > > > > >> > >> > > Yes, but how does this relate to "0000" mode for > > > >> > "register_driver()"? > > > >> > >> > > Maybe you can describe some use case so it will become more > > > >> > >> > > clear? > > > >> > >> > > Currently ioctl works fine if driver is registered with > > "0000" > > > >> > >> permission > > > >> > >> > > mode. > > > >> > >> > > > > > >> > >> > > Best regards, > > > >> > >> > > Petro > > > >> > >> > > > > > >> > >> > > пт, 28 січ. 2022 р. о 11:39 Xiang Xiao > > > >> > >> > > <[email protected] > > > >> > > > > >> > >> пише: > > > >> > >> > >> > > > >> > >> > >> If we want to do the correct permission check, the ioctl > > > >> > >> > >> handler > > > >> > >> needs to > > > >> > >> > >> check R/W bit by itself based on how the ioctl is > > implemented. > > > >> > >> > >> Or follow up how Linux encode the needed permission into > > each > > > >> > IOCTL: > > > >> > >> > >> > > > >> > >> > > > >> > > > > >> > > > > > > https://github.com/torvalds/linux/blob/master/include/uapi/asm-generic/ioctl.h#L85-L91 > > > >> > >> > >> and let's VFS layer do the check for each driver. > > > >> > >> > >> > > > >> > >> > >> On Fri, Jan 28, 2022 at 5:14 PM Petro Karashchenko < > > > >> > >> > >> [email protected]> wrote: > > > >> > >> > >> > > > >> > >> > >> > Hello team, > > > >> > >> > >> > > > > >> > >> > >> > Recently I have noticed that there are many places in > code > > > >> where > > > >> > >> > >> > register_driver() is called with non-zero mode with file > > > >> > operation > > > >> > >> > >> > structures that have neither read nor write APIs > > > implemented. > > > >> For > > > >> > >> > >> > example "ret = register_driver(path, &opamp_fops, 0444, > > > >> > >> > >> > dev);" > > > >> > >> > >> > while > > > >> > >> > >> > opamp_fops has only "opamp_open", "opamp_close" and > > > >> "opamp_ioctl" > > > >> > >> > >> > implemented. I made a PR to fix it > > > >> > >> > >> > https://github.com/apache/incubator-nuttx/pull/5347 and > > > >> > >> > >> > change > > > >> > >> > >> > mode > > > >> > >> > >> > from "0444" to "0000", but want to ask if anyone sees > any > > > >> > drawback > > > >> > >> in > > > >> > >> > >> > such an approach? Maybe I'm missing something? > > > >> > >> > >> > > > > >> > >> > >> > Best regards, > > > >> > >> > >> > Petro > > > >> > >> > >> > > > > >> > >> > > > > > >> > >> > > > >> > > > > > >> > > > > >> > > > > > > > > > >
