lkml.org 
[lkml]   [2018]   [Dec]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH -manpage 2/2] memfd_create.2: Update manpage with new memfd F_SEAL_FUTURE_WRITE seal
Date
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

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
man2/memfd_create.2 | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/man2/memfd_create.2 b/man2/memfd_create.2
index 3cd392d1b4d9..fce2bf8d0fff 100644
--- a/man2/memfd_create.2
+++ b/man2/memfd_create.2
@@ -280,7 +280,15 @@ in order to restrict further modifications on the file.
(If placing the seal
.BR F_SEAL_WRITE ,
then it will be necessary to first unmap the shared writable mapping
-created in the previous step.)
+created in the previous step. Otherwise, behavior similar to
+.BR F_SEAL_WRITE
+can be achieved, by using
+.BR F_SEAL_FUTURE_WRITE
+which will prevent future writes via
+.BR mmap (2)
+and
+.BR write (2)
+from succeeding, while keeping existing shared writable mappings).
.IP 4.
A second process obtains a file descriptor for the
.BR tmpfs (5)
@@ -425,6 +433,7 @@ main(int argc, char *argv[])
fprintf(stderr, "\\t\\tg \- F_SEAL_GROW\\n");
fprintf(stderr, "\\t\\ts \- F_SEAL_SHRINK\\n");
fprintf(stderr, "\\t\\tw \- F_SEAL_WRITE\\n");
+ fprintf(stderr, "\\t\\tW \- F_SEAL_FUTURE_WRITE\\n");
fprintf(stderr, "\\t\\tS \- F_SEAL_SEAL\\n");
exit(EXIT_FAILURE);
}
@@ -463,6 +472,8 @@ main(int argc, char *argv[])
seals |= F_SEAL_SHRINK;
if (strchr(seals_arg, \(aqw\(aq) != NULL)
seals |= F_SEAL_WRITE;
+ if (strchr(seals_arg, \(aqW\(aq) != NULL)
+ seals |= F_SEAL_FUTURE_WRITE;
if (strchr(seals_arg, \(aqS\(aq) != NULL)
seals |= F_SEAL_SEAL;

@@ -518,6 +529,8 @@ main(int argc, char *argv[])
printf(" GROW");
if (seals & F_SEAL_WRITE)
printf(" WRITE");
+ if (seals & F_SEAL_FUTURE_WRITE)
+ printf(" FUTURE_WRITE");
if (seals & F_SEAL_SHRINK)
printf(" SHRINK");
printf("\\n");
--
2.20.0.rc1.387.gf8505762e3-goog
\
 
 \ /
  Last update: 2018-12-12 23:06    [W:0.025 / U:0.640 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site