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authorDavid Hildenbrand <david@redhat.com>2021-04-22 12:53:00 +0200
committerDavid Hildenbrand <david@redhat.com>2021-09-03 18:42:01 +0200
commit42be8b42535183f84df99acbaf799e38724348f3 (patch)
tree426f6416dabd00c8ba0fa5e78b49f7d3ff7df7fa /fs
parent7d2a07b769330c34b4deabeed939325c77a7ec2f (diff)
binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib()
uselib() is the legacy systemcall for loading shared libraries. Nowadays, applications use dlopen() to load shared libraries, completely implemented in user space via mmap(). For example, glibc uses MAP_COPY to mmap shared libraries. While this maps to MAP_PRIVATE | MAP_DENYWRITE on Linux, Linux ignores any MAP_DENYWRITE specification from user space in mmap. With this change, all remaining in-tree users of MAP_DENYWRITE use it to map an executable. We will be able to open shared libraries loaded via uselib() writable, just as we already can via dlopen() from user space. This is one step into the direction of removing MAP_DENYWRITE from the kernel. This can be considered a minor user space visible change. Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Christian König <christian.koenig@amd.com> Signed-off-by: David Hildenbrand <david@redhat.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/binfmt_aout.c2
-rw-r--r--fs/binfmt_elf.c2
2 files changed, 2 insertions, 2 deletions
diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
index 145917f734fe..d29de971d3f3 100644
--- a/fs/binfmt_aout.c
+++ b/fs/binfmt_aout.c
@@ -309,7 +309,7 @@ static int load_aout_library(struct file *file)
/* Now use mmap to map the library into memory. */
error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
PROT_READ | PROT_WRITE | PROT_EXEC,
- MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
+ MAP_FIXED | MAP_PRIVATE;
N_TXTOFF(ex));
retval = error;
if (error != start_addr)
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 439ed81e755a..6d2c79533631 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1384,7 +1384,7 @@ static int load_elf_library(struct file *file)
(eppnt->p_filesz +
ELF_PAGEOFFSET(eppnt->p_vaddr)),
PROT_READ | PROT_WRITE | PROT_EXEC,
- MAP_FIXED_NOREPLACE | MAP_PRIVATE | MAP_DENYWRITE,
+ MAP_FIXED_NOREPLACE | MAP_PRIVATE,
(eppnt->p_offset -
ELF_PAGEOFFSET(eppnt->p_vaddr)));
if (error != ELF_PAGESTART(eppnt->p_vaddr))