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43b45063 |
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21-Mar-2023 |
Christian Brauner <brauner@kernel.org> |
open: return EINVAL for O_DIRECTORY | O_CREAT After a couple of years and multiple LTS releases we received a report that the behavior of O_DIRECTORY | O_CREAT changed starting with v5.7. On kernels prior to v5.7 combinations of O_DIRECTORY, O_CREAT, O_EXCL had the following semantics: (1) open("/tmp/d", O_DIRECTORY | O_CREAT) * d doesn't exist: create regular file * d exists and is a regular file: ENOTDIR * d exists and is a directory: EISDIR (2) open("/tmp/d", O_DIRECTORY | O_CREAT | O_EXCL) * d doesn't exist: create regular file * d exists and is a regular file: EEXIST * d exists and is a directory: EEXIST (3) open("/tmp/d", O_DIRECTORY | O_EXCL) * d doesn't exist: ENOENT * d exists and is a regular file: ENOTDIR * d exists and is a directory: open directory On kernels since to v5.7 combinations of O_DIRECTORY, O_CREAT, O_EXCL have the following semantics: (1) open("/tmp/d", O_DIRECTORY | O_CREAT) * d doesn't exist: ENOTDIR (create regular file) * d exists and is a regular file: ENOTDIR * d exists and is a directory: EISDIR (2) open("/tmp/d", O_DIRECTORY | O_CREAT | O_EXCL) * d doesn't exist: ENOTDIR (create regular file) * d exists and is a regular file: EEXIST * d exists and is a directory: EEXIST (3) open("/tmp/d", O_DIRECTORY | O_EXCL) * d doesn't exist: ENOENT * d exists and is a regular file: ENOTDIR * d exists and is a directory: open directory This is a fairly substantial semantic change that userspace didn't notice until Pedro took the time to deliberately figure out corner cases. Since no one noticed this breakage we can somewhat safely assume that O_DIRECTORY | O_CREAT combinations are likely unused. The v5.7 breakage is especially weird because while ENOTDIR is returned indicating failure a regular file is actually created. This doesn't make a lot of sense. Time was spent finding potential users of this combination. Searching on codesearch.debian.net showed that codebases often express semantical expectations about O_DIRECTORY | O_CREAT which are completely contrary to what our code has done and currently does. The expectation often is that this particular combination would create and open a directory. This suggests users who tried to use that combination would stumble upon the counterintuitive behavior no matter if pre-v5.7 or post v5.7 and quickly realize neither semantics give them what they want. For some examples see the code examples in [1] to [3] and the discussion in [4]. There are various ways to address this issue. The lazy/simple option would be to restore the pre-v5.7 behavior and to just live with that bug forever. But since there's a real chance that the O_DIRECTORY | O_CREAT quirk isn't relied upon we should try to get away with murder(ing bad semantics) first. If we need to Frankenstein pre-v5.7 behavior later so be it. So let's simply return EINVAL categorically for O_DIRECTORY | O_CREAT combinations. In addition to cleaning up the old bug this also opens up the possiblity to make that flag combination do something more intuitive in the future. Starting with this commit the following semantics apply: (1) open("/tmp/d", O_DIRECTORY | O_CREAT) * d doesn't exist: EINVAL * d exists and is a regular file: EINVAL * d exists and is a directory: EINVAL (2) open("/tmp/d", O_DIRECTORY | O_CREAT | O_EXCL) * d doesn't exist: EINVAL * d exists and is a regular file: EINVAL * d exists and is a directory: EINVAL (3) open("/tmp/d", O_DIRECTORY | O_EXCL) * d doesn't exist: ENOENT * d exists and is a regular file: ENOTDIR * d exists and is a directory: open directory One additional note, O_TMPFILE is implemented as: #define __O_TMPFILE 020000000 #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY) #define O_TMPFILE_MASK (__O_TMPFILE | O_DIRECTORY | O_CREAT) For older kernels it was important to return an explicit error when O_TMPFILE wasn't supported. So O_TMPFILE requires that O_DIRECTORY is raised alongside __O_TMPFILE. It also enforced that O_CREAT wasn't specified. Since O_DIRECTORY | O_CREAT could be used to create a regular allowing that combination together with __O_TMPFILE would've meant that false positives were possible, i.e., that a regular file was created instead of a O_TMPFILE. This could've been used to trick userspace into thinking it operated on a O_TMPFILE when it wasn't. Now that we block O_DIRECTORY | O_CREAT completely the check for O_CREAT in the __O_TMPFILE branch via if ((flags & O_TMPFILE_MASK) != O_TMPFILE) can be dropped. Instead we can simply check verify that O_DIRECTORY is raised via if (!(flags & O_DIRECTORY)) and explain this in two comments. As Aleksa pointed out O_PATH is unaffected by this change since it always returned EINVAL if O_CREAT was specified - with or without O_DIRECTORY. Link: https://lore.kernel.org/lkml/20230320071442.172228-1-pedro.falcato@gmail.com Link: https://sources.debian.org/src/flatpak/1.14.4-1/subprojects/libglnx/glnx-dirfd.c/?hl=324#L324 [1] Link: https://sources.debian.org/src/flatpak-builder/1.2.3-1/subprojects/libglnx/glnx-shutil.c/?hl=251#L251 [2] Link: https://sources.debian.org/src/ostree/2022.7-2/libglnx/glnx-dirfd.c/?hl=324#L324 [3] Link: https://www.openwall.com/lists/oss-security/2014/11/26/14 [4] Reported-by: Pedro Falcato <pedro.falcato@gmail.com> Cc: Aleksa Sarai <cyphar@cyphar.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
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6f05e014 |
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22-Jul-2022 |
Slark Xiao <slark_xiao@163.com> |
uapi: asm-generic: fcntl: Fix typo 'the the' in comment Replace 'the the' with 'the' in the comment. Signed-off-by: Slark Xiao <slark_xiao@163.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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9b31e608 |
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15-Jul-2022 |
Florian Fainelli <f.fainelli@gmail.com> |
tools: Fixed MIPS builds due to struct flock re-definition Building perf for MIPS failed after 9f79b8b72339 ("uapi: simplify __ARCH_FLOCK{,64}_PAD a little") with the following error: CC /home/fainelli/work/buildroot/output/bmips/build/linux-custom/tools/perf/trace/beauty/fcntl.o In file included from ../../../../host/mipsel-buildroot-linux-gnu/sysroot/usr/include/asm/fcntl.h:77, from ../include/uapi/linux/fcntl.h:5, from trace/beauty/fcntl.c:10: ../include/uapi/asm-generic/fcntl.h:188:8: error: redefinition of 'struct flock' struct flock { ^~~~~ In file included from ../include/uapi/linux/fcntl.h:5, from trace/beauty/fcntl.c:10: ../../../../host/mipsel-buildroot-linux-gnu/sysroot/usr/include/asm/fcntl.h:63:8: note: originally defined here struct flock { ^~~~~ This is due to the local copy under tools/include/uapi/asm-generic/fcntl.h including the toolchain's kernel headers which already define 'struct flock' and define HAVE_ARCH_STRUCT_FLOCK to future inclusions make a decision as to whether re-defining 'struct flock' is appropriate or not. Make sure what do not re-define 'struct flock' when HAVE_ARCH_STRUCT_FLOCK is already defined. Fixes: 9f79b8b72339 ("uapi: simplify __ARCH_FLOCK{,64}_PAD a little") Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> [arnd: sync with include/uapi/asm-generic/fcntl.h as well] Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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306f7cc1 |
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05-Apr-2022 |
Christoph Hellwig <hch@lst.de> |
uapi: always define F_GETLK64/F_SETLK64/F_SETLKW64 in fcntl.h The F_GETLK64/F_SETLK64/F_SETLKW64 fcntl opcodes are only implemented for the 32-bit syscall APIs, but are also needed for compat handling on 64-bit kernels. Consolidate them in unistd.h instead of definining the internal compat definitions in compat.h, which is rather error prone (e.g. parisc gets the values wrong currently). Note that before this change they were never visible to userspace due to the fact that CONFIG_64BIT is only set for kernel builds. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Guo Ren <guoren@kernel.org> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Tested-by: Heiko Stuebner <heiko@sntech.de> Link: https://lore.kernel.org/r/20220405071314.3225832-3-guoren@kernel.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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9f79b8b7 |
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05-Apr-2022 |
Christoph Hellwig <hch@lst.de> |
uapi: simplify __ARCH_FLOCK{,64}_PAD a little Don't bother to define the symbols empty, just don't use them. That makes the intent a little more clear. Remove the unused HAVE_ARCH_STRUCT_FLOCK64 define and merge the 32-bit mips struct flock into the generic one. Add a new __ARCH_FLOCK_EXTRA_SYSID macro following the style of __ARCH_FLOCK_PAD to avoid having a separate definition just for one architecture. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Guo Ren <guoren@kernel.org> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Tested-by: Heiko Stuebner <heiko@sntech.de> Link: https://lore.kernel.org/r/20220405071314.3225832-2-guoren@kernel.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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84d1d8a1 |
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18-Jul-2017 |
Arnaldo Carvalho de Melo <acme@redhat.com> |
tools include uapi asm-generic: Grab a copy of fcntl.h We'll need defines for beautifying fcntl arguments that are not available in older distros, these: trace/beauty/fcntl.c: In function 'syscall_arg__scnprintf_fcntl_arg': trace/beauty/fcntl.c:93: error: 'F_OFD_SETLK' undeclared (first use in this function) trace/beauty/fcntl.c:93: error: (Each undeclared identifier is reported only once trace/beauty/fcntl.c:93: error: for each function it appears in.) trace/beauty/fcntl.c:93: error: 'F_OFD_SETLKW' undeclared (first use in this function) trace/beauty/fcntl.c:93: error: 'F_OFD_GETLK' undeclared (first use in this function) trace/beauty/fcntl.c:94: error: 'F_GETOWN_EX' undeclared (first use in this function) trace/beauty/fcntl.c:94: error: 'F_SETOWN_EX' undeclared (first use in this function) Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Wang Nan <wangnan0@huawei.com> Link: http://lkml.kernel.org/n/tip-gvlw67a47e9z65jdunj4je5s@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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