diff options
| author | Rich Felker <dalias@libc.org> | 2020-08-31 11:32:08 -0400 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2024-01-22 15:33:37 +0100 |
| commit | 73fa7547c70b32cc69685f79be31135797734eb6 (patch) | |
| tree | 61eca04ae3dafb7132f40baa1e73b27dd9f3f949 /include/linux/fs.h | |
| parent | 9e3f1c59367515e7e40675fe83645a131c05039d (diff) | |
| download | linux-stable-73fa7547c70b32cc69685f79be31135797734eb6.tar.gz linux-stable-73fa7547c70b32cc69685f79be31135797734eb6.tar.bz2 linux-stable-73fa7547c70b32cc69685f79be31135797734eb6.zip | |
vfs: add RWF_NOAPPEND flag for pwritev2
The pwrite function, originally defined by POSIX (thus the "p"), is
defined to ignore O_APPEND and write at the offset passed as its
argument. However, historically Linux honored O_APPEND if set and
ignored the offset. This cannot be changed due to stability policy,
but is documented in the man page as a bug.
Now that there's a pwritev2 syscall providing a superset of the pwrite
functionality that has a flags argument, the conforming behavior can
be offered to userspace via a new flag. Since pwritev2 checks flag
validity (in kiocb_set_rw_flags) and reports unknown ones with
EOPNOTSUPP, callers will not get wrong behavior on old kernels that
don't support the new flag; the error is reported and the caller can
decide how to handle it.
Signed-off-by: Rich Felker <dalias@libc.org>
Link: https://lore.kernel.org/r/20200831153207.GO3265@brightrain.aerifal.cx
Reviewed-by: Jann Horn <jannh@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'include/linux/fs.h')
| -rw-r--r-- | include/linux/fs.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index ed5966a70495..4f7cfda29143 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3335,6 +3335,8 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags) return 0; if (unlikely(flags & ~RWF_SUPPORTED)) return -EOPNOTSUPP; + if (unlikely((flags & RWF_APPEND) && (flags & RWF_NOAPPEND))) + return -EINVAL; if (flags & RWF_NOWAIT) { if (!(ki->ki_filp->f_mode & FMODE_NOWAIT)) @@ -3345,6 +3347,12 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags) if (flags & RWF_SYNC) kiocb_flags |= IOCB_DSYNC; + if ((flags & RWF_NOAPPEND) && (ki->ki_flags & IOCB_APPEND)) { + if (IS_APPEND(file_inode(ki->ki_filp))) + return -EPERM; + ki->ki_flags &= ~IOCB_APPEND; + } + ki->ki_flags |= kiocb_flags; return 0; } |