[PATCH -manpage 1/2] fcntl.2: Update manpage with new memfd F_SEAL_FUTURE_WRITE seal
From: Joel Fernandes (Google) <hidden>
Date: 2018-11-20 05:26:14
Also in:
linux-kselftest, linux-man, linux-mm, lkml
Subsystem:
the rest · Maintainer:
Linus Torvalds
More details of the seal can be found in the LKML patch: https://lore.kernel.org/lkml/20181120052137.74317-1-joel@joelfernandes.org/T/#t (local) Signed-off-by: Joel Fernandes (Google) <redacted> --- man2/fcntl.2 | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/man2/fcntl.2 b/man2/fcntl.2
index 03533d65b49d..54772f94964c 100644
--- a/man2/fcntl.2
+++ b/man2/fcntl.2@@ -1525,6 +1525,21 @@ Furthermore, if there are any asynchronous I/O operations .RB ( io_submit (2)) pending on the file, all outstanding writes will be discarded. +.TP +.BR F_SEAL_FUTURE_WRITE +If this seal is set, the contents of the file can be modified only from +existing writeable mappings that were created prior to the seal being set. +Any attempt to create a new writeable mapping on the memfd via +.BR mmap (2) +will fail with +.BR EPERM. +Also any attempts to write to the memfd via +.BR write (2) +will fail with +.BR EPERM. +This is useful in situations where existing writable mapped regions need to be +kept intact while preventing any future writes. For example, to share a +read-only memory buffer to other processes that only the sender can write to. .\" .SS File read/write hints Write lifetime hints can be used to inform the kernel about the relative
--
2.19.1.1215.g8438c0b245-goog