From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Joel Fernandes (Google)" Subject: [PATCH -manpage 2/2] memfd_create.2: Update manpage with new memfd F_SEAL_FUTURE_WRITE seal Date: Mon, 19 Nov 2018 21:25:45 -0800 Message-ID: <20181120052545.76560-2-joel@joelfernandes.org> References: <20181120052545.76560-1-joel@joelfernandes.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20181120052545.76560-1-joel@joelfernandes.org> Sender: linux-kernel-owner@vger.kernel.org To: linux-man@vger.kernel.org Cc: "Joel Fernandes (Google)" , Andrew Morton , Andy Lutomirski , Hugh Dickins , Jann Horn , John Stultz , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Matthew Wilcox , Mike Kravetz , Shuah Khan , Stephen Rothwell List-Id: linux-api@vger.kernel.org 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) --- 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"); -- 2.19.1.1215.g8438c0b245-goog