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Bottomley" , Helge Deller , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , "David S. Miller" , Andreas Larsson , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Chris Zankel , Max Filippov , Alexander Viro , =?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?= , =?utf-8?Q?G=C3=BCnther?= Noack , Arnd Bergmann , Pali =?utf-8?B?Um9ow6Fy?= , Paul Moore , James Morris , "Serge E. Hallyn" , linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-xfs@vger.kernel.org Subject: Re: [PATCH v4 3/3] fs: introduce getfsxattrat and setfsxattrat syscalls Message-ID: <20250424-zuspielen-luxus-3d49b600c3bf@brauner> References: <20250321-xattrat-syscall-v4-0-3e82e6fb3264@kernel.org> <20250321-xattrat-syscall-v4-3-3e82e6fb3264@kernel.org> <20250422-abbekommen-begierde-bcf48dd74a2e@brauner> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Wed, Apr 23, 2025 at 11:53:25AM +0200, Jan Kara wrote: > On Tue 22-04-25 16:59:02, Christian Brauner wrote: > > On Fri, Mar 21, 2025 at 08:48:42PM +0100, Andrey Albershteyn wrote: > > > From: Andrey Albershteyn > > > > > > Introduce getfsxattrat and setfsxattrat syscalls to manipulate inode > > > extended attributes/flags. The syscalls take parent directory fd and > > > path to the child together with struct fsxattr. > > > > > > This is an alternative to FS_IOC_FSSETXATTR ioctl with a difference > > > that file don't need to be open as we can reference it with a path > > > instead of fd. By having this we can manipulated inode extended > > > attributes not only on regular files but also on special ones. This > > > is not possible with FS_IOC_FSSETXATTR ioctl as with special files > > > we can not call ioctl() directly on the filesystem inode using fd. > > > > > > This patch adds two new syscalls which allows userspace to get/set > > > extended inode attributes on special files by using parent directory > > > and a path - *at() like syscall. > > > > > > CC: linux-api@vger.kernel.org > > > CC: linux-fsdevel@vger.kernel.org > > > CC: linux-xfs@vger.kernel.org > > > Signed-off-by: Andrey Albershteyn > > > Acked-by: Arnd Bergmann > ... > > > + struct fsxattr __user *, ufsx, size_t, usize, > > > + unsigned int, at_flags) > > > +{ > > > + struct fileattr fa = {}; > > > + struct path filepath; > > > + int error; > > > + unsigned int lookup_flags = 0; > > > + struct filename *name; > > > + struct fsxattr fsx = {}; > > > + > > > + BUILD_BUG_ON(sizeof(struct fsxattr) < FSXATTR_SIZE_VER0); > > > + BUILD_BUG_ON(sizeof(struct fsxattr) != FSXATTR_SIZE_LATEST); > > > + > > > + if ((at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0) > > > + return -EINVAL; > > > + > > > + if (!(at_flags & AT_SYMLINK_NOFOLLOW)) > > > + lookup_flags |= LOOKUP_FOLLOW; > > > + > > > + if (at_flags & AT_EMPTY_PATH) > > > + lookup_flags |= LOOKUP_EMPTY; > > > + > > > + if (usize > PAGE_SIZE) > > > + return -E2BIG; > > > + > > > + if (usize < FSXATTR_SIZE_VER0) > > > + return -EINVAL; > > > + > > > + name = getname_maybe_null(filename, at_flags); > > > + if (!name) { > > > > This is broken as it doesn't handle AT_FDCWD correctly. You need: > > > > name = getname_maybe_null(filename, at_flags); > > if (IS_ERR(name)) > > return PTR_ERR(name); > > > > if (!name && dfd >= 0) { > > CLASS(fd, f)(dfd); > > Ah, you're indeed right that if dfd == AT_FDCWD and filename == NULL, the > we should operate on cwd but we'd bail with error here. I've missed that > during my review. But as far as I've checked the same bug is there in > path_setxattrat() and path_getxattrat() so we should fix this there as > well? Yes, please!