* [PATCH] Implement fchmodat4 system call
@ 2015-05-11 2:07 William Orr
2015-05-11 2:07 ` [PATCH 1/2] Implement fchmodat4 syscall William Orr
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: William Orr @ 2015-05-11 2:07 UTC (permalink / raw)
To: linux-kernel
Hey,
Currently, Linux's fchmodat(2) doesn't honor the flags argument. To bring it
more in-line with POSIX and other implementations, this patch adds fchmodat4,
which honors the flags argument, and implements the same flags as fchownat(2).
This makes it possible to chmod a file without following symlinks, without
having to call open(2) on a file with O_NOFOLLOW. This is heavily based off
of Andrew Ayer's work in 2012, and is sent with his permission. Let me know
if this can be applied.
Please CC me, since I'm not subscribed to this list.
Thanks,
William Orr
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH 1/2] Implement fchmodat4 syscall 2015-05-11 2:07 [PATCH] Implement fchmodat4 system call William Orr @ 2015-05-11 2:07 ` William Orr 2015-05-12 8:48 ` Michael Kerrisk 2015-05-11 2:07 ` [PATCH 2/2] Define syscall number for fchmodat4 William Orr 2015-05-12 8:48 ` [PATCH] Implement fchmodat4 system call Michael Kerrisk 2 siblings, 1 reply; 6+ messages in thread From: William Orr @ 2015-05-11 2:07 UTC (permalink / raw) To: linux-kernel; +Cc: William Orr Adds fchmodat4 which more closely matches POSIX by taking 4 arguments, including the flags argument. flags are the same as fchownat(2), implementing both AT_SYMLINK_NOFOLLOW and AT_EMPTY_PATH Based heavily off of Andrew Ayer's patch from 2012. --- fs/open.c | 19 +++++++++++++++++-- include/linux/syscalls.h | 2 ++ 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/fs/open.c b/fs/open.c index 98e5a52..00dd0f7 100644 --- a/fs/open.c +++ b/fs/open.c @@ -504,6 +504,9 @@ static int chmod_common(struct path *path, umode_t mode) struct iattr newattrs; int error; + if (S_ISLNK(inode->i_mode)) + return -EOPNOTSUPP; + error = mnt_want_write(path->mnt); if (error) return error; @@ -541,9 +544,21 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode) { + return sys_fchmodat4(dfd, filename, mode, 0); +} + +SYSCALL_DEFINE4(fchmodat4, int, dfd, const char __user *, filename, umode_t, mode, int, flags) +{ struct path path; int error; - unsigned int lookup_flags = LOOKUP_FOLLOW; + unsigned int lookup_flags; + + if (flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) + return -EINVAL; + + lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW; + if (flags & AT_EMPTY_PATH) + lookup_flags |= LOOKUP_EMPTY; retry: error = user_path_at(dfd, filename, lookup_flags, &path); if (!error) { @@ -559,7 +574,7 @@ retry: SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode) { - return sys_fchmodat(AT_FDCWD, filename, mode); + return sys_fchmodat4(AT_FDCWD, filename, mode, 0); } static int chown_common(struct path *path, uid_t user, gid_t group) diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 76d1e38..d6e9602 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -769,6 +769,8 @@ asmlinkage long sys_futimesat(int dfd, const char __user *filename, asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode); asmlinkage long sys_fchmodat(int dfd, const char __user * filename, umode_t mode); +asmlinkage long sys_fchmodat4(int dfd, const char __user * filename, + umode_t mode, int flags); asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group, int flag); asmlinkage long sys_openat(int dfd, const char __user *filename, int flags, -- 2.1.0 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] Implement fchmodat4 syscall 2015-05-11 2:07 ` [PATCH 1/2] Implement fchmodat4 syscall William Orr @ 2015-05-12 8:48 ` Michael Kerrisk 0 siblings, 0 replies; 6+ messages in thread From: Michael Kerrisk @ 2015-05-12 8:48 UTC (permalink / raw) To: William Orr Cc: Linux Kernel, Al Viro, Miklos Szeredi, Linux API, Linux-Fsdevel, Andrew Ayer [expanding CC] On Mon, May 11, 2015 at 4:07 AM, William Orr <will@worrbase.com> wrote: > Adds fchmodat4 which more closely matches POSIX by taking 4 arguments, > including the flags argument. flags are the same as fchownat(2), implementing > both AT_SYMLINK_NOFOLLOW and AT_EMPTY_PATH > > Based heavily off of Andrew Ayer's patch from 2012. > --- > fs/open.c | 19 +++++++++++++++++-- > include/linux/syscalls.h | 2 ++ > 2 files changed, 19 insertions(+), 2 deletions(-) > > diff --git a/fs/open.c b/fs/open.c > index 98e5a52..00dd0f7 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -504,6 +504,9 @@ static int chmod_common(struct path *path, umode_t mode) > struct iattr newattrs; > int error; > > + if (S_ISLNK(inode->i_mode)) > + return -EOPNOTSUPP; > + > error = mnt_want_write(path->mnt); > if (error) > return error; > @@ -541,9 +544,21 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) > > SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode) > { > + return sys_fchmodat4(dfd, filename, mode, 0); > +} > + > +SYSCALL_DEFINE4(fchmodat4, int, dfd, const char __user *, filename, umode_t, mode, int, flags) > +{ > struct path path; > int error; > - unsigned int lookup_flags = LOOKUP_FOLLOW; > + unsigned int lookup_flags; > + > + if (flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) > + return -EINVAL; > + > + lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW; > + if (flags & AT_EMPTY_PATH) > + lookup_flags |= LOOKUP_EMPTY; > retry: > error = user_path_at(dfd, filename, lookup_flags, &path); > if (!error) { > @@ -559,7 +574,7 @@ retry: > > SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode) > { > - return sys_fchmodat(AT_FDCWD, filename, mode); > + return sys_fchmodat4(AT_FDCWD, filename, mode, 0); > } > > static int chown_common(struct path *path, uid_t user, gid_t group) > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > index 76d1e38..d6e9602 100644 > --- a/include/linux/syscalls.h > +++ b/include/linux/syscalls.h > @@ -769,6 +769,8 @@ asmlinkage long sys_futimesat(int dfd, const char __user *filename, > asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode); > asmlinkage long sys_fchmodat(int dfd, const char __user * filename, > umode_t mode); > +asmlinkage long sys_fchmodat4(int dfd, const char __user * filename, > + umode_t mode, int flags); > asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user, > gid_t group, int flag); > asmlinkage long sys_openat(int dfd, const char __user *filename, int flags, > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface", http://blog.man7.org/ ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 2/2] Define syscall number for fchmodat4 2015-05-11 2:07 [PATCH] Implement fchmodat4 system call William Orr 2015-05-11 2:07 ` [PATCH 1/2] Implement fchmodat4 syscall William Orr @ 2015-05-11 2:07 ` William Orr 2015-05-12 8:49 ` Michael Kerrisk 2015-05-12 8:48 ` [PATCH] Implement fchmodat4 system call Michael Kerrisk 2 siblings, 1 reply; 6+ messages in thread From: William Orr @ 2015-05-11 2:07 UTC (permalink / raw) To: linux-kernel; +Cc: William Orr --- arch/x86/syscalls/syscall_32.tbl | 1 + arch/x86/syscalls/syscall_64.tbl | 1 + include/uapi/asm-generic/unistd.h | 4 +++- 3 files changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl index ef8187f..cc8ada8 100644 --- a/arch/x86/syscalls/syscall_32.tbl +++ b/arch/x86/syscalls/syscall_32.tbl @@ -365,3 +365,4 @@ 356 i386 memfd_create sys_memfd_create 357 i386 bpf sys_bpf 358 i386 execveat sys_execveat stub32_execveat +359 i386 fchmodat4 sys_fchmodat4 diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl index 9ef32d5..bbf8c6b 100644 --- a/arch/x86/syscalls/syscall_64.tbl +++ b/arch/x86/syscalls/syscall_64.tbl @@ -329,6 +329,7 @@ 320 common kexec_file_load sys_kexec_file_load 321 common bpf sys_bpf 322 64 execveat stub_execveat +323 common fchmodat4 sys_fchmodat4 # # x32-specific system call numbers start at 512 to avoid cache impact diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h index e016bd9..6e362a2 100644 --- a/include/uapi/asm-generic/unistd.h +++ b/include/uapi/asm-generic/unistd.h @@ -709,9 +709,11 @@ __SYSCALL(__NR_memfd_create, sys_memfd_create) __SYSCALL(__NR_bpf, sys_bpf) #define __NR_execveat 281 __SC_COMP(__NR_execveat, sys_execveat, compat_sys_execveat) +#define __NR_fchmodat4 282 +__SYSCALL(__NR_fchmodat4, sys_fchmodat4); #undef __NR_syscalls -#define __NR_syscalls 282 +#define __NR_syscalls 283 /* * All syscalls below here should go away really, -- 2.1.0 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2] Define syscall number for fchmodat4 2015-05-11 2:07 ` [PATCH 2/2] Define syscall number for fchmodat4 William Orr @ 2015-05-12 8:49 ` Michael Kerrisk 0 siblings, 0 replies; 6+ messages in thread From: Michael Kerrisk @ 2015-05-12 8:49 UTC (permalink / raw) To: William Orr Cc: Linux Kernel, Andrew Ayer, Al Viro, Linux-Fsdevel, Miklos Szeredi, Linux API [expanding CC] On Mon, May 11, 2015 at 4:07 AM, William Orr <will@worrbase.com> wrote: > --- > arch/x86/syscalls/syscall_32.tbl | 1 + > arch/x86/syscalls/syscall_64.tbl | 1 + > include/uapi/asm-generic/unistd.h | 4 +++- > 3 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl > index ef8187f..cc8ada8 100644 > --- a/arch/x86/syscalls/syscall_32.tbl > +++ b/arch/x86/syscalls/syscall_32.tbl > @@ -365,3 +365,4 @@ > 356 i386 memfd_create sys_memfd_create > 357 i386 bpf sys_bpf > 358 i386 execveat sys_execveat stub32_execveat > +359 i386 fchmodat4 sys_fchmodat4 > diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl > index 9ef32d5..bbf8c6b 100644 > --- a/arch/x86/syscalls/syscall_64.tbl > +++ b/arch/x86/syscalls/syscall_64.tbl > @@ -329,6 +329,7 @@ > 320 common kexec_file_load sys_kexec_file_load > 321 common bpf sys_bpf > 322 64 execveat stub_execveat > +323 common fchmodat4 sys_fchmodat4 > > # > # x32-specific system call numbers start at 512 to avoid cache impact > diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h > index e016bd9..6e362a2 100644 > --- a/include/uapi/asm-generic/unistd.h > +++ b/include/uapi/asm-generic/unistd.h > @@ -709,9 +709,11 @@ __SYSCALL(__NR_memfd_create, sys_memfd_create) > __SYSCALL(__NR_bpf, sys_bpf) > #define __NR_execveat 281 > __SC_COMP(__NR_execveat, sys_execveat, compat_sys_execveat) > +#define __NR_fchmodat4 282 > +__SYSCALL(__NR_fchmodat4, sys_fchmodat4); > > #undef __NR_syscalls > -#define __NR_syscalls 282 > +#define __NR_syscalls 283 > > /* > * All syscalls below here should go away really, > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface", http://blog.man7.org/ ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Implement fchmodat4 system call 2015-05-11 2:07 [PATCH] Implement fchmodat4 system call William Orr 2015-05-11 2:07 ` [PATCH 1/2] Implement fchmodat4 syscall William Orr 2015-05-11 2:07 ` [PATCH 2/2] Define syscall number for fchmodat4 William Orr @ 2015-05-12 8:48 ` Michael Kerrisk 2 siblings, 0 replies; 6+ messages in thread From: Michael Kerrisk @ 2015-05-12 8:48 UTC (permalink / raw) To: William Orr Cc: Linux Kernel, Andrew Ayer, Al Viro, Linux-Fsdevel, Linux API, Miklos Szeredi [CC += linux-api@vger.kernel.org] Hello William, Since this is a kernel-user-space API change, please CC linux-api@. The kernel source file Documentation/SubmitChecklist notes that all Linux kernel patches that change userspace interfaces should be CCed to linux-api@vger.kernel.org, so that the various parties who are interested in API changes are informed. For further information, see https://www.kernel.org/doc/man-pages/linux-api-ml.html Aside from that, I've added a few other people/lists to CC that seem likely to be relevant. Some additional comments below. On Mon, May 11, 2015 at 4:07 AM, William Orr <will@worrbase.com> wrote: > Hey, > > Currently, Linux's fchmodat(2) doesn't honor the flags argument. To bring it > more in-line with POSIX and other implementations, this patch adds fchmodat4, > which honors the flags argument, and implements the same flags as fchownat(2). > > This makes it possible to chmod a file without following symlinks, without > having to call open(2) on a file with O_NOFOLLOW. This is heavily based off > of Andrew Ayer's work in 2012, and is sent with his permission. Let me know > if this can be applied. > > Please CC me, since I'm not subscribed to this list. This seems an obviously sensible addition, and it was an obvious mistake not to have a 'flags' argument in the original system call (https://lwn.net/Articles/585415/). As well as getting us a proper POSIX compliant API (and one that is consistent with other implementations, such as FreeBSD), it allows for future behavior expansion via the 'flags' argument. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface", http://blog.man7.org/ ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2015-05-12 8:49 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2015-05-11 2:07 [PATCH] Implement fchmodat4 system call William Orr 2015-05-11 2:07 ` [PATCH 1/2] Implement fchmodat4 syscall William Orr 2015-05-12 8:48 ` Michael Kerrisk 2015-05-11 2:07 ` [PATCH 2/2] Define syscall number for fchmodat4 William Orr 2015-05-12 8:49 ` Michael Kerrisk 2015-05-12 8:48 ` [PATCH] Implement fchmodat4 system call Michael Kerrisk
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