| Message ID | 20190930183316.10190-4-cyphar@cyphar.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | namei: openat2(2) path resolution restrictions | expand |
On 2019-10-01, kbuild test robot <lkp@intel.com> wrote: > Hi Aleksa, > > Thank you for the patch! Yet something to improve: > > [auto build test ERROR on linus/master] > [cannot apply to v5.4-rc1 next-20190930] > [if your patch is applied to the wrong git tree, please drop us a note to help > improve the system. BTW, we also suggest to use '--base' option to specify the > base tree in git format-patch, please see https://stackoverflow.com/a/37406982] > > url: https://github.com/0day-ci/linux/commits/Aleksa-Sarai/namei-openat2-2-path-resolution-restrictions/20191001-025628 > config: sparc-allyesconfig (attached as .config) > compiler: sparc64-linux-gcc (GCC) 7.4.0 > reproduce: > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross > chmod +x ~/bin/make.cross > # save the attached .config to linux build tree > GCC_VERSION=7.4.0 make.cross ARCH=sparc > > If you fix the issue, kindly add following tag > Reported-by: kbuild test robot <lkp@intel.com> > > All error/warnings (new ones prefixed by >>): > > In file included from include/linux/kernel.h:11:0, > from include/linux/list.h:9, > from include/linux/wait.h:7, > from include/linux/wait_bit.h:8, > from include/linux/fs.h:6, > from include/uapi/linux/aio_abi.h:31, > from include/linux/syscalls.h:74, > from fs/fcntl.c:8: > fs/fcntl.c: In function 'fcntl_init': > >> include/linux/compiler.h:350:38: error: call to '__compiletime_assert_1037' declared with attribute error: BUILD_BUG_ON failed: 22 - 1 != HWEIGHT32( (VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) | __FMODE_EXEC | __FMODE_NONOTIFY) > _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) > ^ > include/linux/compiler.h:331:4: note: in definition of macro '__compiletime_assert' > prefix ## suffix(); \ > ^~~~~~ > include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert' > _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) > ^~~~~~~~~~~~~~~~~~~ > include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' > #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > ^~~~~~~~~~~~~~~~~~ > include/linux/build_bug.h:50:2: note: in expansion of macro 'BUILD_BUG_ON_MSG' > BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) > ^~~~~~~~~~~~~~~~ > >> fs/fcntl.c:1034:2: note: in expansion of macro 'BUILD_BUG_ON' > BUILD_BUG_ON(22 - 1 /* for O_RDONLY being 0 */ != > ^~~~~~~~~~~~ This is because 0x4000000 is used by FMODE_NONOTIFY. The fix is simple, and I'll include it in the next version. > vim +/__compiletime_assert_1037 +350 include/linux/compiler.h > > 9a8ab1c39970a4 Daniel Santos 2013-02-21 336 > 9a8ab1c39970a4 Daniel Santos 2013-02-21 337 #define _compiletime_assert(condition, msg, prefix, suffix) \ > 9a8ab1c39970a4 Daniel Santos 2013-02-21 338 __compiletime_assert(condition, msg, prefix, suffix) > 9a8ab1c39970a4 Daniel Santos 2013-02-21 339 > 9a8ab1c39970a4 Daniel Santos 2013-02-21 340 /** > 9a8ab1c39970a4 Daniel Santos 2013-02-21 341 * compiletime_assert - break build and emit msg if condition is false > 9a8ab1c39970a4 Daniel Santos 2013-02-21 342 * @condition: a compile-time constant condition to check > 9a8ab1c39970a4 Daniel Santos 2013-02-21 343 * @msg: a message to emit if condition is false > 9a8ab1c39970a4 Daniel Santos 2013-02-21 344 * > 9a8ab1c39970a4 Daniel Santos 2013-02-21 345 * In tradition of POSIX assert, this macro will break the build if the > 9a8ab1c39970a4 Daniel Santos 2013-02-21 346 * supplied condition is *false*, emitting the supplied error message if the > 9a8ab1c39970a4 Daniel Santos 2013-02-21 347 * compiler has support to do so. > 9a8ab1c39970a4 Daniel Santos 2013-02-21 348 */ > 9a8ab1c39970a4 Daniel Santos 2013-02-21 349 #define compiletime_assert(condition, msg) \ > 9a8ab1c39970a4 Daniel Santos 2013-02-21 @350 _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) > 9a8ab1c39970a4 Daniel Santos 2013-02-21 351 > > :::::: The code at line 350 was first introduced by commit > :::::: 9a8ab1c39970a4938a72d94e6fd13be88a797590 bug.h, compiler.h: introduce compiletime_assert & BUILD_BUG_ON_MSG > > :::::: TO: Daniel Santos <daniel.santos@pobox.com> > :::::: CC: Linus Torvalds <torvalds@linux-foundation.org> > > --- > 0-DAY kernel test infrastructure Open Source Technology Center > https://lists.01.org/pipermail/kbuild-all Intel Corporation
diff --git a/arch/alpha/include/uapi/asm/fcntl.h b/arch/alpha/include/uapi/asm/fcntl.h index 50bdc8e8a271..1f879bade68b 100644 --- a/arch/alpha/include/uapi/asm/fcntl.h +++ b/arch/alpha/include/uapi/asm/fcntl.h @@ -34,6 +34,7 @@ #define O_PATH 040000000 #define __O_TMPFILE 0100000000 +#define O_EMPTYPATH 0200000000 #define F_GETLK 7 #define F_SETLK 8 diff --git a/arch/parisc/include/uapi/asm/fcntl.h b/arch/parisc/include/uapi/asm/fcntl.h index 03ce20e5ad7d..5d709058a76f 100644 --- a/arch/parisc/include/uapi/asm/fcntl.h +++ b/arch/parisc/include/uapi/asm/fcntl.h @@ -2,26 +2,27 @@ #ifndef _PARISC_FCNTL_H #define _PARISC_FCNTL_H -#define O_APPEND 000000010 -#define O_BLKSEEK 000000100 /* HPUX only */ -#define O_CREAT 000000400 /* not fcntl */ -#define O_EXCL 000002000 /* not fcntl */ -#define O_LARGEFILE 000004000 -#define __O_SYNC 000100000 +#define O_APPEND 0000000010 +#define O_BLKSEEK 0000000100 /* HPUX only */ +#define O_CREAT 0000000400 /* not fcntl */ +#define O_EXCL 0000002000 /* not fcntl */ +#define O_LARGEFILE 0000004000 +#define __O_SYNC 0000100000 #define O_SYNC (__O_SYNC|O_DSYNC) -#define O_NONBLOCK 000200004 /* HPUX has separate NDELAY & NONBLOCK */ -#define O_NOCTTY 000400000 /* not fcntl */ -#define O_DSYNC 001000000 /* HPUX only */ -#define O_RSYNC 002000000 /* HPUX only */ -#define O_NOATIME 004000000 -#define O_CLOEXEC 010000000 /* set close_on_exec */ - -#define O_DIRECTORY 000010000 /* must be a directory */ -#define O_NOFOLLOW 000000200 /* don't follow links */ -#define O_INVISIBLE 004000000 /* invisible I/O, for DMAPI/XDSM */ - -#define O_PATH 020000000 -#define __O_TMPFILE 040000000 +#define O_NONBLOCK 0000200004 /* HPUX has separate NDELAY & NONBLOCK */ +#define O_NOCTTY 0000400000 /* not fcntl */ +#define O_DSYNC 0001000000 /* HPUX only */ +#define O_RSYNC 0002000000 /* HPUX only */ +#define O_NOATIME 0004000000 +#define O_CLOEXEC 0010000000 /* set close_on_exec */ + +#define O_DIRECTORY 0000010000 /* must be a directory */ +#define O_NOFOLLOW 0000000200 /* don't follow links */ +#define O_INVISIBLE 0004000000 /* invisible I/O, for DMAPI/XDSM */ + +#define O_PATH 0020000000 +#define __O_TMPFILE 0040000000 +#define O_EMPTYPATH 0100000000 #define F_GETLK64 8 #define F_SETLK64 9 diff --git a/arch/sparc/include/uapi/asm/fcntl.h b/arch/sparc/include/uapi/asm/fcntl.h index 67dae75e5274..dc86c9eaf950 100644 --- a/arch/sparc/include/uapi/asm/fcntl.h +++ b/arch/sparc/include/uapi/asm/fcntl.h @@ -37,6 +37,7 @@ #define O_PATH 0x1000000 #define __O_TMPFILE 0x2000000 +#define O_EMPTYPATH 0x4000000 #define F_GETOWN 5 /* for sockets. */ #define F_SETOWN 6 /* for sockets. */ diff --git a/fs/fcntl.c b/fs/fcntl.c index 3d40771e8e7c..4cf05a2fd162 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -1031,7 +1031,7 @@ static int __init fcntl_init(void) * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY * is defined as O_NONBLOCK on some platforms and not on others. */ - BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ != + BUILD_BUG_ON(22 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32( (VALID_OPEN_FLAGS & ~(O_NONBLOCK | O_NDELAY)) | __FMODE_EXEC | __FMODE_NONOTIFY)); diff --git a/fs/namei.c b/fs/namei.c index 0e3a47e6f12c..bfeac55b23b7 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -3567,6 +3567,24 @@ static int trailing_magiclink(struct nameidata *nd, int acc_mode, return may_open_magiclink(upgrade_mask, acc_mode); } +static int do_emptypath(struct nameidata *nd, const struct open_flags *op, + struct file *file) +{ + int error; + /* We don't support AT_FDCWD (since O_PATH is disallowed here). */ + struct fd f = fdget_raw(nd->dfd); + + if (!f.file) + return -EBADF; + + /* Apply trailing_magiclink()-like restrictions. */ + error = may_open_magiclink(f.file->f_mode, op->acc_mode); + if (!error) + error = vfs_open(&f.file->f_path, file); + fdput(f); + return error; +} + static struct file *path_openat(struct nameidata *nd, const struct open_flags *op, unsigned flags) { @@ -3579,6 +3597,8 @@ static struct file *path_openat(struct nameidata *nd, if (unlikely(file->f_flags & __O_TMPFILE)) { error = do_tmpfile(nd, flags, op, file); + } else if (unlikely(file->f_flags & O_EMPTYPATH)) { + error = do_emptypath(nd, op, file); } else if (unlikely(file->f_flags & O_PATH)) { /* Inlined path_lookupat() with a trailing_magiclink() check. */ fmode_t opath_mask = op->opath_mask; diff --git a/fs/open.c b/fs/open.c index 44704f9184cc..a45fd4cbda1f 100644 --- a/fs/open.c +++ b/fs/open.c @@ -1023,6 +1023,8 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o lookup_flags |= LOOKUP_DIRECTORY; if (!(flags & O_NOFOLLOW)) lookup_flags |= LOOKUP_FOLLOW; + if (flags & O_EMPTYPATH) + lookup_flags |= LOOKUP_EMPTY; op->lookup_flags = lookup_flags; return 0; } @@ -1084,14 +1086,17 @@ long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode) { struct open_flags op; int fd = build_open_flags(flags, mode, &op); + int empty = 0; struct filename *tmp; if (fd) return fd; - tmp = getname(filename); + tmp = getname_flags(filename, op.lookup_flags, &empty); if (IS_ERR(tmp)) return PTR_ERR(tmp); + if (!empty) + op.open_flag &= ~O_EMPTYPATH; fd = get_unused_fd_flags(flags); if (fd >= 0) { diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h index d019df946cb2..2868ae6c8fc1 100644 --- a/include/linux/fcntl.h +++ b/include/linux/fcntl.h @@ -9,7 +9,7 @@ (O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | \ O_APPEND | O_NDELAY | O_NONBLOCK | O_NDELAY | __O_SYNC | O_DSYNC | \ FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | \ - O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE) + O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE | O_EMPTYPATH) #ifndef force_o_largefile #define force_o_largefile() (!IS_ENABLED(CONFIG_ARCH_32BIT_OFF_T)) diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h index 9dc0bf0c5a6e..ae6862f69cc2 100644 --- a/include/uapi/asm-generic/fcntl.h +++ b/include/uapi/asm-generic/fcntl.h @@ -89,6 +89,10 @@ #define __O_TMPFILE 020000000 #endif +#ifndef O_EMPTYPATH +#define O_EMPTYPATH 040000000 +#endif + /* a horrid kludge trying to make sure that this will fail on old kernels */ #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY) #define O_TMPFILE_MASK (__O_TMPFILE | O_DIRECTORY | O_CREAT)
Userspace has made use of /proc/self/fd very liberally to allow for descriptors to be re-opened. There are a wide variety of uses for this feature, but it has always required constructing a pathname and could not be done without procfs mounted. The obvious solution for this is to extend openat(2) to have an AT_EMPTY_PATH-equivalent -- O_EMPTYPATH. Now that descriptor re-opening has been made safe through the new magic-link resolution restrictions, we can replicate these restrictions for O_EMPTYPATH. In particular, we only allow "upgrading" the file descriptor if the corresponding FMODE_PATH_* bit is set (or the FMODE_{READ,WRITE} cases for non-O_PATH file descriptors). When doing openat(O_EMPTYPATH|O_PATH), O_PATH takes precedence and O_EMPTYPATH is ignored. Very few users ever have a need to O_PATH re-open an existing file descriptor, and so accommodating them at the expense of further complicating O_PATH makes little sense. Ultimately, if users ask for this we can always add RESOLVE_EMPTY_PATH to resolveat(2) in the future. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> --- arch/alpha/include/uapi/asm/fcntl.h | 1 + arch/parisc/include/uapi/asm/fcntl.h | 39 ++++++++++++++-------------- arch/sparc/include/uapi/asm/fcntl.h | 1 + fs/fcntl.c | 2 +- fs/namei.c | 20 ++++++++++++++ fs/open.c | 7 ++++- include/linux/fcntl.h | 2 +- include/uapi/asm-generic/fcntl.h | 4 +++ 8 files changed, 54 insertions(+), 22 deletions(-)