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authorDavid Herrmann <dh.herrmann@gmail.com>2014-08-18 13:05:48 +0200
committerDavid Herrmann <dh.herrmann@gmail.com>2014-08-18 13:05:48 +0200
commit23972f4244f7609658c2a17f85508d50e4739990 (patch)
treeecc7b9895abf0c193cae5bf2deb6dcdfe8b77c04
parentc7dab73a5fa6e775813765fe925caaa7c4e549fa (diff)
memfd: map unsealed files as MAP_SHARED
We need to map sealed files as MAP_PRIVATE so far as the kernel treats MAP_SHARED as writable mapping (you can run mprotect(PROT_WRITE) at any time on those). However, unsealed files must be mapped as MAP_SHARED. Otherwise, we never end up writing to the real file.
-rw-r--r--src/shared/memfd.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/src/shared/memfd.c b/src/shared/memfd.c
index 6804b42361..d94c6268dd 100644
--- a/src/shared/memfd.c
+++ b/src/shared/memfd.c
@@ -176,7 +176,11 @@ int sd_memfd_map(sd_memfd *m, uint64_t offset, size_t size, void **p) {
if (sealed < 0)
return sealed;
- q = mmap(NULL, size, sealed ? PROT_READ : PROT_READ|PROT_WRITE, MAP_PRIVATE, m->fd, offset);
+ if (sealed)
+ q = mmap(NULL, size, PROT_READ, MAP_PRIVATE, m->fd, offset);
+ else
+ q = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, m->fd, offset);
+
if (q == MAP_FAILED)
return -errno;