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 <xiaoxiang781...@gmail.com> 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 < > petro.karashche...@gmail.com> wrote: > >> So Alan do you suggest to remove inode_checkflags? >> >> On Fri, Apr 1, 2022, 4:13 PM Alan Carvalho de Assis <acas...@gmail.com> >> 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 <petro.karashche...@gmail.com> 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 >> > > <petro.karashche...@gmail.com> >> > > 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 >> > >> <acas...@gmail.com >> > >> > >> 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 <petro.karashche...@gmail.com> >> 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 >> > >> > > <xiaoxiang781...@gmail.com >> > >> > >> 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 < >> > >> > >> petro.karashche...@gmail.com> 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 >> > >> > >> > >> > >> > > >> > >> >> > > >> > >> >
