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| author | Alexey Gladkov <legion@kernel.org> | 2023-07-11 18:16:04 +0200 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2023-07-27 12:24:09 +0200 |
| commit | 09da082b07bbae1c11d9560c8502800039aebcea (patch) | |
| tree | fabe0c66e6a009ffbaa40c75b20f14eca2e411e0 /fs/open.c | |
| parent | 06a0213977dc5f8345c1222183b8fafac1a8a524 (diff) | |
| download | linux-09da082b07bbae1c11d9560c8502800039aebcea.tar.gz | |
fs: Add fchmodat2()
On the userspace side fchmodat(3) is implemented as a wrapper
function which implements the POSIX-specified interface. This
interface differs from the underlying kernel system call, which does not
have a flags argument. Most implementations require procfs [1][2].
There doesn't appear to be a good userspace workaround for this issue
but the implementation in the kernel is pretty straight-forward.
The new fchmodat2() syscall allows to pass the AT_SYMLINK_NOFOLLOW flag,
unlike existing fchmodat.
[1] https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/fchmodat.c;h=17eca54051ee28ba1ec3f9aed170a62630959143;hb=a492b1e5ef7ab50c6fdd4e4e9879ea5569ab0a6c#l35
[2] https://git.musl-libc.org/cgit/musl/tree/src/stat/fchmodat.c?id=718f363bc2067b6487900eddc9180c84e7739f80#n28
Co-developed-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Message-Id: <f2a846ef495943c5d101011eebcf01179d0c7b61.1689092120.git.legion@kernel.org>
[brauner: pre reviews, do flag conversion in do_fchmodat() directly]
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs/open.c')
| -rw-r--r-- | fs/open.c | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/fs/open.c b/fs/open.c index 0c55c8e7f837d..e52d78e5a3330 100644 --- a/fs/open.c +++ b/fs/open.c @@ -671,11 +671,18 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) return err; } -static int do_fchmodat(int dfd, const char __user *filename, umode_t mode) +static int do_fchmodat(int dfd, const char __user *filename, umode_t mode, + unsigned int flags) { struct path path; int error; - unsigned int lookup_flags = LOOKUP_FOLLOW; + unsigned int lookup_flags; + + if (unlikely(flags & ~AT_SYMLINK_NOFOLLOW)) + return -EINVAL; + + lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW; + retry: error = user_path_at(dfd, filename, lookup_flags, &path); if (!error) { @@ -689,15 +696,21 @@ retry: return error; } +SYSCALL_DEFINE4(fchmodat2, int, dfd, const char __user *, filename, + umode_t, mode, unsigned int, flags) +{ + return do_fchmodat(dfd, filename, mode, flags); +} + SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode) { - return do_fchmodat(dfd, filename, mode); + return do_fchmodat(dfd, filename, mode, 0); } SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode) { - return do_fchmodat(AT_FDCWD, filename, mode); + return do_fchmodat(AT_FDCWD, filename, mode, 0); } /* |