On Fri, Mar 21, 2025 at 08:48:42PM +0100, Andrey Albershteyn wrote: > From: Andrey Albershteyn <aalbe...@redhat.com> > > 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-...@vger.kernel.org > CC: linux-fsde...@vger.kernel.org > CC: linux-...@vger.kernel.org > Signed-off-by: Andrey Albershteyn <aalbe...@redhat.com> > Acked-by: Arnd Bergmann <a...@arndb.de> > --- > arch/alpha/kernel/syscalls/syscall.tbl | 2 + > arch/arm/tools/syscall.tbl | 2 + > arch/arm64/tools/syscall_32.tbl | 2 + > arch/m68k/kernel/syscalls/syscall.tbl | 2 + > arch/microblaze/kernel/syscalls/syscall.tbl | 2 + > arch/mips/kernel/syscalls/syscall_n32.tbl | 2 + > arch/mips/kernel/syscalls/syscall_n64.tbl | 2 + > arch/mips/kernel/syscalls/syscall_o32.tbl | 2 + > arch/parisc/kernel/syscalls/syscall.tbl | 2 + > arch/powerpc/kernel/syscalls/syscall.tbl | 2 + > arch/s390/kernel/syscalls/syscall.tbl | 2 + > arch/sh/kernel/syscalls/syscall.tbl | 2 + > arch/sparc/kernel/syscalls/syscall.tbl | 2 + > arch/x86/entry/syscalls/syscall_32.tbl | 2 + > arch/x86/entry/syscalls/syscall_64.tbl | 2 + > arch/xtensa/kernel/syscalls/syscall.tbl | 2 + > fs/inode.c | 130 > ++++++++++++++++++++++++++++ > include/linux/syscalls.h | 6 ++ > include/uapi/asm-generic/unistd.h | 8 +- > include/uapi/linux/fs.h | 3 + > 20 files changed, 178 insertions(+), 1 deletion(-) > > diff --git a/arch/alpha/kernel/syscalls/syscall.tbl > b/arch/alpha/kernel/syscalls/syscall.tbl > index > c59d53d6d3f3490f976ca179ddfe02e69265ae4d..4b9e687494c16b60c6fd6ca1dc4d6564706a7e25 > 100644 > --- a/arch/alpha/kernel/syscalls/syscall.tbl > +++ b/arch/alpha/kernel/syscalls/syscall.tbl > @@ -506,3 +506,5 @@ > 574 common getxattrat sys_getxattrat > 575 common listxattrat sys_listxattrat > 576 common removexattrat sys_removexattrat > +577 common getfsxattrat sys_getfsxattrat > +578 common setfsxattrat sys_setfsxattrat > diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl > index > 49eeb2ad8dbd8e074c6240417693f23fb328afa8..66466257f3c2debb3e2299f0b608c6740c98cab2 > 100644 > --- a/arch/arm/tools/syscall.tbl > +++ b/arch/arm/tools/syscall.tbl > @@ -481,3 +481,5 @@ > 464 common getxattrat sys_getxattrat > 465 common listxattrat sys_listxattrat > 466 common removexattrat sys_removexattrat > +467 common getfsxattrat sys_getfsxattrat > +468 common setfsxattrat sys_setfsxattrat > diff --git a/arch/arm64/tools/syscall_32.tbl b/arch/arm64/tools/syscall_32.tbl > index > 69a829912a05eb8a3e21ed701d1030e31c0148bc..9c516118b154811d8d11d5696f32817430320dbf > 100644 > --- a/arch/arm64/tools/syscall_32.tbl > +++ b/arch/arm64/tools/syscall_32.tbl > @@ -478,3 +478,5 @@ > 464 common getxattrat sys_getxattrat > 465 common listxattrat sys_listxattrat > 466 common removexattrat sys_removexattrat > +467 common getfsxattrat sys_getfsxattrat > +468 common setfsxattrat sys_setfsxattrat > diff --git a/arch/m68k/kernel/syscalls/syscall.tbl > b/arch/m68k/kernel/syscalls/syscall.tbl > index > f5ed71f1910d09769c845c2d062d99ee0449437c..159476387f394a92ee5e29db89b118c630372db2 > 100644 > --- a/arch/m68k/kernel/syscalls/syscall.tbl > +++ b/arch/m68k/kernel/syscalls/syscall.tbl > @@ -466,3 +466,5 @@ > 464 common getxattrat sys_getxattrat > 465 common listxattrat sys_listxattrat > 466 common removexattrat sys_removexattrat > +467 common getfsxattrat sys_getfsxattrat > +468 common setfsxattrat sys_setfsxattrat > diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl > b/arch/microblaze/kernel/syscalls/syscall.tbl > index > 680f568b77f2cbefc3eacb2517f276041f229b1e..a6d59ee740b58cacf823702003cf9bad17c0d3b7 > 100644 > --- a/arch/microblaze/kernel/syscalls/syscall.tbl > +++ b/arch/microblaze/kernel/syscalls/syscall.tbl > @@ -472,3 +472,5 @@ > 464 common getxattrat sys_getxattrat > 465 common listxattrat sys_listxattrat > 466 common removexattrat sys_removexattrat > +467 common getfsxattrat sys_getfsxattrat > +468 common setfsxattrat sys_setfsxattrat > diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl > b/arch/mips/kernel/syscalls/syscall_n32.tbl > index > 0b9b7e25b69ad592642f8533bee9ccfe95ce9626..cfe38fcebe1a0279e11751378d3e71c5ec6b6569 > 100644 > --- a/arch/mips/kernel/syscalls/syscall_n32.tbl > +++ b/arch/mips/kernel/syscalls/syscall_n32.tbl > @@ -405,3 +405,5 @@ > 464 n32 getxattrat sys_getxattrat > 465 n32 listxattrat sys_listxattrat > 466 n32 removexattrat sys_removexattrat > +467 n32 getfsxattrat sys_getfsxattrat > +468 n32 setfsxattrat sys_setfsxattrat > diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl > b/arch/mips/kernel/syscalls/syscall_n64.tbl > index > c844cd5cda620b2809a397cdd6f4315ab6a1bfe2..29a0c5974d1aa2f01e33edc0252d75fb97abe230 > 100644 > --- a/arch/mips/kernel/syscalls/syscall_n64.tbl > +++ b/arch/mips/kernel/syscalls/syscall_n64.tbl > @@ -381,3 +381,5 @@ > 464 n64 getxattrat sys_getxattrat > 465 n64 listxattrat sys_listxattrat > 466 n64 removexattrat sys_removexattrat > +467 n64 getfsxattrat sys_getfsxattrat > +468 n64 setfsxattrat sys_setfsxattrat > diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl > b/arch/mips/kernel/syscalls/syscall_o32.tbl > index > 349b8aad1159f404103bd2057a1e64e9bf309f18..6c00436807c57c492ba957fcd59af1202231cf80 > 100644 > --- a/arch/mips/kernel/syscalls/syscall_o32.tbl > +++ b/arch/mips/kernel/syscalls/syscall_o32.tbl > @@ -454,3 +454,5 @@ > 464 o32 getxattrat sys_getxattrat > 465 o32 listxattrat sys_listxattrat > 466 o32 removexattrat sys_removexattrat > +467 o32 getfsxattrat sys_getfsxattrat > +468 o32 setfsxattrat sys_setfsxattrat > diff --git a/arch/parisc/kernel/syscalls/syscall.tbl > b/arch/parisc/kernel/syscalls/syscall.tbl > index > d9fc94c869657fcfbd7aca1d5f5abc9fae2fb9d8..b3578fac43d6b65167787fcc97d2d09f5a9828e7 > 100644 > --- a/arch/parisc/kernel/syscalls/syscall.tbl > +++ b/arch/parisc/kernel/syscalls/syscall.tbl > @@ -465,3 +465,5 @@ > 464 common getxattrat sys_getxattrat > 465 common listxattrat sys_listxattrat > 466 common removexattrat sys_removexattrat > +467 common getfsxattrat sys_getfsxattrat > +468 common setfsxattrat sys_setfsxattrat > diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl > b/arch/powerpc/kernel/syscalls/syscall.tbl > index > d8b4ab78bef076bd50d49b87dea5060fd8c1686a..808045d82c9465c3bfa96b15947546efe5851e9a > 100644 > --- a/arch/powerpc/kernel/syscalls/syscall.tbl > +++ b/arch/powerpc/kernel/syscalls/syscall.tbl > @@ -557,3 +557,5 @@ > 464 common getxattrat sys_getxattrat > 465 common listxattrat sys_listxattrat > 466 common removexattrat sys_removexattrat > +467 common getfsxattrat sys_getfsxattrat > +468 common setfsxattrat sys_setfsxattrat > diff --git a/arch/s390/kernel/syscalls/syscall.tbl > b/arch/s390/kernel/syscalls/syscall.tbl > index > e9115b4d8b635b846e5c9ad6ce229605323723a5..78dfc2c184d4815baf8a9e61c546c9936d58a47c > 100644 > --- a/arch/s390/kernel/syscalls/syscall.tbl > +++ b/arch/s390/kernel/syscalls/syscall.tbl > @@ -469,3 +469,5 @@ > 464 common getxattrat sys_getxattrat > sys_getxattrat > 465 common listxattrat sys_listxattrat > sys_listxattrat > 466 common removexattrat sys_removexattrat > sys_removexattrat > +467 common getfsxattrat sys_getfsxattrat > sys_getfsxattrat > +468 common setfsxattrat sys_setfsxattrat > sys_setfsxattrat > diff --git a/arch/sh/kernel/syscalls/syscall.tbl > b/arch/sh/kernel/syscalls/syscall.tbl > index > c8cad33bf250ea110de37bd1407f5a43ec5e38f2..d5a5c8339f0ed25ea07c4aba90351d352033c8a0 > 100644 > --- a/arch/sh/kernel/syscalls/syscall.tbl > +++ b/arch/sh/kernel/syscalls/syscall.tbl > @@ -470,3 +470,5 @@ > 464 common getxattrat sys_getxattrat > 465 common listxattrat sys_listxattrat > 466 common removexattrat sys_removexattrat > +467 common getfsxattrat sys_getfsxattrat > +468 common setfsxattrat sys_setfsxattrat > diff --git a/arch/sparc/kernel/syscalls/syscall.tbl > b/arch/sparc/kernel/syscalls/syscall.tbl > index > 727f99d333b304b3db0711953a3d91ece18a28eb..817dcd8603bcbffc47f3f59aa3b74b16486453d0 > 100644 > --- a/arch/sparc/kernel/syscalls/syscall.tbl > +++ b/arch/sparc/kernel/syscalls/syscall.tbl > @@ -512,3 +512,5 @@ > 464 common getxattrat sys_getxattrat > 465 common listxattrat sys_listxattrat > 466 common removexattrat sys_removexattrat > +467 common getfsxattrat sys_getfsxattrat > +468 common setfsxattrat sys_setfsxattrat > diff --git a/arch/x86/entry/syscalls/syscall_32.tbl > b/arch/x86/entry/syscalls/syscall_32.tbl > index > 4d0fb2fba7e208ae9455459afe11e277321d9f74..b4842c027c5d00c0236b2ba89387c5e2267447bd > 100644 > --- a/arch/x86/entry/syscalls/syscall_32.tbl > +++ b/arch/x86/entry/syscalls/syscall_32.tbl > @@ -472,3 +472,5 @@ > 464 i386 getxattrat sys_getxattrat > 465 i386 listxattrat sys_listxattrat > 466 i386 removexattrat sys_removexattrat > +467 i386 getfsxattrat sys_getfsxattrat > +468 i386 setfsxattrat sys_setfsxattrat > diff --git a/arch/x86/entry/syscalls/syscall_64.tbl > b/arch/x86/entry/syscalls/syscall_64.tbl > index > 5eb708bff1c791debd6cfc5322583b2ae53f6437..b6f0a7236aaee624cf9b484239a1068085a8ffe1 > 100644 > --- a/arch/x86/entry/syscalls/syscall_64.tbl > +++ b/arch/x86/entry/syscalls/syscall_64.tbl > @@ -390,6 +390,8 @@ > 464 common getxattrat sys_getxattrat > 465 common listxattrat sys_listxattrat > 466 common removexattrat sys_removexattrat > +467 common getfsxattrat sys_getfsxattrat > +468 common setfsxattrat sys_setfsxattrat > > # > # Due to a historical design error, certain syscalls are numbered differently > diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl > b/arch/xtensa/kernel/syscalls/syscall.tbl > index > 37effc1b134eea061f2c350c1d68b4436b65a4dd..425d56be337d1de22f205ac503df61ff86224fee > 100644 > --- a/arch/xtensa/kernel/syscalls/syscall.tbl > +++ b/arch/xtensa/kernel/syscalls/syscall.tbl > @@ -437,3 +437,5 @@ > 464 common getxattrat sys_getxattrat > 465 common listxattrat sys_listxattrat > 466 common removexattrat sys_removexattrat > +467 common getfsxattrat sys_getfsxattrat > +468 common setfsxattrat sys_setfsxattrat > diff --git a/fs/inode.c b/fs/inode.c > index > 6b4c77268fc0ecace4ac78a9ca777fbffc277f4a..811debf379ab299f287ed90863277cfda27db30c > 100644 > --- a/fs/inode.c > +++ b/fs/inode.c
I really dislike the name fsxattr for a lot of reasons but it definitely shouldn't go in inode.c. Just add a new fs/file_attr.c file and move all the relevant helpers from fs/ioctl.c in there and then add the system calls. Otherwise it's just all very confusing. > @@ -23,6 +23,9 @@ > #include <linux/rw_hint.h> > #include <linux/seq_file.h> > #include <linux/debugfs.h> > +#include <linux/syscalls.h> > +#include <linux/fileattr.h> > +#include <linux/namei.h> > #include <trace/events/writeback.h> > #define CREATE_TRACE_POINTS > #include <trace/events/timestamp.h> > @@ -2953,3 +2956,130 @@ umode_t mode_strip_sgid(struct mnt_idmap *idmap, > return mode & ~S_ISGID; > } > EXPORT_SYMBOL(mode_strip_sgid); > + > +SYSCALL_DEFINE5(getfsxattrat, int, dfd, const char __user *, filename, This is really misnamed. It will end up confusing userspace to no end: getxattr() getxattrat() getfsxattrat() Please name this file_setattr() and file_getattr(). There's also no need for the *at() prefix. We've never been consistent with that. We have plent of system calls that to fd+path without having an *at() prefix. And here it's especially unneeded because there's no pre-existing system calls that would even force the use of that prefix. > + 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); > + CLASS(fd, f)(dfd); > + > + if (fd_empty(f)) > + return -EBADF; I'm pretty sure you can just do a: path = fd_file(f_to)->f_path; path_get(&path); and then the vfs_fileattr_get() call and the path_put() call can be shared between the two branches. Note that you can also use: struct path path __free(path_put) = NULL; and then the cleanup infrastructure will handle the path_put() for you. > + error = vfs_fileattr_get(file_dentry(fd_file(f)), &fa); > + } else { > + error = filename_lookup(dfd, name, lookup_flags, &filepath, > + NULL); > + if (error) > + goto out; > + error = vfs_fileattr_get(filepath.dentry, &fa); > + path_put(&filepath); > + } > + if (error == -ENOIOCTLCMD) > + error = -EOPNOTSUPP; > + if (!error) { > + fileattr_to_fsxattr(&fa, &fsx); > + error = copy_struct_to_user(ufsx, usize, &fsx, > + sizeof(struct fsxattr), NULL); > + } > +out: > + putname(name); > + return error; > +} > + > +SYSCALL_DEFINE5(setfsxattrat, int, dfd, const char __user *, filename, > + 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 mnt_idmap *idmap; > + struct dentry *dentry; > + struct vfsmount *mnt; > + 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; > + > + error = copy_struct_from_user(&fsx, sizeof(struct fsxattr), ufsx, > usize); > + if (error) > + return error; > + > + fsxattr_to_fileattr(&fsx, &fa); > + > + name = getname_maybe_null(filename, at_flags); > + if (!name) { Same comment as above. > + CLASS(fd, f)(dfd); > + > + if (fd_empty(f)) > + return -EBADF; > + > + idmap = file_mnt_idmap(fd_file(f)); > + dentry = file_dentry(fd_file(f)); > + mnt = fd_file(f)->f_path.mnt; This is a UAF. fd_file(f)->f_path.mnt and file_dentry(fd_file(f)) will get auto cleaned at the end of the scope. By the time you call vfs_fileattr_set() nothing pins them anymore... In general, same comment about unifying the branches as for the get case via path_get() as above. And just keep the path around don't store mount and dentry separately. > + } else { > + error = filename_lookup(dfd, name, lookup_flags, &filepath, > + NULL); > + if (error) > + return error; > + > + idmap = mnt_idmap(filepath.mnt); > + dentry = filepath.dentry; > + mnt = filepath.mnt; > + } > + > + error = mnt_want_write(mnt); > + if (!error) { > + error = vfs_fileattr_set(idmap, dentry, &fa); > + if (error == -ENOIOCTLCMD) > + error = -EOPNOTSUPP; > + mnt_drop_write(mnt); > + } > + > + path_put(&filepath); > + return error; > +} > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > index > c6333204d45130eb022f6db460eea34a1f6e91db..e242ea39b3e63a8008bc777764b616fd63bd40c4 > 100644 > --- a/include/linux/syscalls.h > +++ b/include/linux/syscalls.h > @@ -371,6 +371,12 @@ asmlinkage long sys_removexattrat(int dfd, const char > __user *path, > asmlinkage long sys_lremovexattr(const char __user *path, > const char __user *name); > asmlinkage long sys_fremovexattr(int fd, const char __user *name); > +asmlinkage long sys_getfsxattrat(int dfd, const char __user *filename, > + struct fsxattr __user *ufsx, size_t usize, > + unsigned int at_flags); > +asmlinkage long sys_setfsxattrat(int dfd, const char __user *filename, > + struct fsxattr __user *ufsx, size_t usize, > + unsigned int at_flags); > asmlinkage long sys_getcwd(char __user *buf, unsigned long size); > asmlinkage long sys_eventfd2(unsigned int count, int flags); > asmlinkage long sys_epoll_create1(int flags); > diff --git a/include/uapi/asm-generic/unistd.h > b/include/uapi/asm-generic/unistd.h > index > 88dc393c2bca38c0fa1b3fae579f7cfe4931223c..50be2e1007bc2779120d05c6e9512a689f86779c > 100644 > --- a/include/uapi/asm-generic/unistd.h > +++ b/include/uapi/asm-generic/unistd.h > @@ -850,8 +850,14 @@ __SYSCALL(__NR_listxattrat, sys_listxattrat) > #define __NR_removexattrat 466 > __SYSCALL(__NR_removexattrat, sys_removexattrat) > > +/* fs/inode.c */ > +#define __NR_getfsxattrat 467 > +__SYSCALL(__NR_getfsxattrat, sys_getfsxattrat) > +#define __NR_setfsxattrat 468 > +__SYSCALL(__NR_setfsxattrat, sys_setfsxattrat) > + > #undef __NR_syscalls > -#define __NR_syscalls 467 > +#define __NR_syscalls 469 > > /* > * 32 bit systems traditionally used different > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h > index > 7539717707337a8cb22396a869baba3bafa08371..aed753e5d50c97da9b895a187fdaecf0477db74b > 100644 > --- a/include/uapi/linux/fs.h > +++ b/include/uapi/linux/fs.h > @@ -139,6 +139,9 @@ struct fsxattr { > unsigned char fsx_pad[8]; > }; > > +#define FSXATTR_SIZE_VER0 28 > +#define FSXATTR_SIZE_LATEST FSXATTR_SIZE_VER0 > + > /* > * Flags for the fsx_xflags field > */ > > -- > 2.47.2 >