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authorAlexey Gladkov <legion@kernel.org>2023-07-11 18:16:04 +0200
committerChristian Brauner <brauner@kernel.org>2023-07-27 12:24:09 +0200
commit09da082b07bbae1c11d9560c8502800039aebcea (patch)
treefabe0c66e6a009ffbaa40c75b20f14eca2e411e0 /fs/open.c
parent06a0213977dc5f8345c1222183b8fafac1a8a524 (diff)
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.c21
1 files changed, 17 insertions, 4 deletions
diff --git a/fs/open.c b/fs/open.c
index 0c55c8e7f837..e52d78e5a333 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);
}
/*