Commit 49624efa authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'denywrite-for-5.15' of git://github.com/davidhildenbrand/linux

Pull MAP_DENYWRITE removal from David Hildenbrand:
 "Remove all in-tree usage of MAP_DENYWRITE from the kernel and remove
  VM_DENYWRITE.

  There are some (minor) user-visible changes:

   - We no longer deny write access to shared libaries loaded via legacy
     uselib(); this behavior matches modern user space e.g. dlopen().

   - We no longer deny write access to the elf interpreter after exec
     completed, treating it just like shared libraries (which it often
     is).

   - We always deny write access to the file linked via /proc/pid/exe:
     sys_prctl(PR_SET_MM_MAP/EXE_FILE) will fail if write access to the
     file cannot be denied, and write access to the file will remain
     denied until the link is effectivel gone (exec, termination,
     sys_prctl(PR_SET_MM_MAP/EXE_FILE)) -- just as if exec'ing the file.

  Cross-compiled for a bunch of architectures (alpha, microblaze, i386,
  s390x, ...) and verified via ltp that especially the relevant tests
  (i.e., creat07 and execve04) continue working as expected"

* tag 'denywrite-for-5.15' of git://github.com/davidhildenbrand/linux:
  fs: update documentation of get_write_access() and friends
  mm: ignore MAP_DENYWRITE in ksys_mmap_pgoff()
  mm: remove VM_DENYWRITE
  binfmt: remove in-tree usage of MAP_DENYWRITE
  kernel/fork: always deny write access to current MM exe_file
  kernel/fork: factor out replacing the current MM exe_file
  binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib()
parents f7464060 592ca09b
......@@ -202,8 +202,7 @@ static int load_aout_binary(struct linux_binprm *bprm)
error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
PROT_READ | PROT_EXEC,
MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE |
MAP_32BIT,
MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
fd_offset);
if (error != N_TXTADDR(ex))
......@@ -211,8 +210,7 @@ static int load_aout_binary(struct linux_binprm *bprm)
error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE |
MAP_32BIT,
MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
fd_offset + ex.a_text);
if (error != N_DATADDR(ex))
return error;
......@@ -293,7 +291,7 @@ 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_32BIT,
MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
N_TXTOFF(ex));
retval = error;
if (error != start_addr)
......
......@@ -221,8 +221,7 @@ static int load_aout_binary(struct linux_binprm * bprm)
}
error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
PROT_READ | PROT_EXEC,
MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
PROT_READ | PROT_EXEC, MAP_FIXED | MAP_PRIVATE,
fd_offset);
if (error != N_TXTADDR(ex))
......@@ -230,7 +229,7 @@ static int load_aout_binary(struct linux_binprm * bprm)
error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE,
MAP_FIXED | MAP_PRIVATE,
fd_offset + ex.a_text);
if (error != N_DATADDR(ex))
return error;
......@@ -309,7 +308,7 @@ 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)
......
......@@ -622,7 +622,7 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
eppnt = interp_elf_phdata;
for (i = 0; i < interp_elf_ex->e_phnum; i++, eppnt++) {
if (eppnt->p_type == PT_LOAD) {
int elf_type = MAP_PRIVATE | MAP_DENYWRITE;
int elf_type = MAP_PRIVATE;
int elf_prot = make_prot(eppnt->p_flags, arch_state,
true, true);
unsigned long vaddr = 0;
......@@ -1070,7 +1070,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
elf_prot = make_prot(elf_ppnt->p_flags, &arch_state,
!!interpreter, false);
elf_flags = MAP_PRIVATE | MAP_DENYWRITE;
elf_flags = MAP_PRIVATE;
vaddr = elf_ppnt->p_vaddr;
/*
......@@ -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))
......
......@@ -1041,7 +1041,7 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
if (phdr->p_flags & PF_W) prot |= PROT_WRITE;
if (phdr->p_flags & PF_X) prot |= PROT_EXEC;
flags = MAP_PRIVATE | MAP_DENYWRITE;
flags = MAP_PRIVATE;
maddr = 0;
switch (params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) {
......
......@@ -1272,7 +1272,9 @@ int begin_new_exec(struct linux_binprm * bprm)
* not visibile until then. This also enables the update
* to be lockless.
*/
set_mm_exe_file(bprm->mm, bprm->file);
retval = set_mm_exe_file(bprm->mm, bprm->file);
if (retval)
goto out;
/* If the binary is not readable then enforce mm->dumpable=0 */
would_dump(bprm, bprm->file);
......
......@@ -619,7 +619,6 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
[ilog2(VM_MAYSHARE)] = "ms",
[ilog2(VM_GROWSDOWN)] = "gd",
[ilog2(VM_PFNMAP)] = "pf",
[ilog2(VM_DENYWRITE)] = "dw",
[ilog2(VM_LOCKED)] = "lo",
[ilog2(VM_IO)] = "io",
[ilog2(VM_SEQ_READ)] = "sr",
......
......@@ -3023,15 +3023,20 @@ static inline void file_end_write(struct file *file)
}
/*
* This is used for regular files where some users -- especially the
* currently executed binary in a process, previously handled via
* VM_DENYWRITE -- cannot handle concurrent write (and maybe mmap
* read-write shared) accesses.
*
* get_write_access() gets write permission for a file.
* put_write_access() releases this write permission.
* This is used for regular files.
* We cannot support write (and maybe mmap read-write shared) accesses and
* MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
* can have the following values:
* 0: no writers, no VM_DENYWRITE mappings
* < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
* > 0: (i_writecount) users are writing to the file.
* deny_write_access() denies write access to a file.
* allow_write_access() re-enables write access to a file.
*
* The i_writecount field of an inode can have the following values:
* 0: no write access, no denied write access
* < 0: (-i_writecount) users that denied write access to the file.
* > 0: (i_writecount) users that have write access to the file.
*
* Normally we operate on that counter with atomic_{inc,dec} and it's safe
* except for the cases where we don't hold i_writecount yet. Then we need to
......
......@@ -281,7 +281,6 @@ extern unsigned int kobjsize(const void *objp);
#define VM_GROWSDOWN 0x00000100 /* general info on the segment */
#define VM_UFFD_MISSING 0x00000200 /* missing pages tracking */
#define VM_PFNMAP 0x00000400 /* Page-ranges managed without "struct page", just pure PFN */
#define VM_DENYWRITE 0x00000800 /* ETXTBSY on write attempts.. */
#define VM_UFFD_WP 0x00001000 /* wrprotect pages tracking */
#define VM_LOCKED 0x00002000
......@@ -2573,7 +2572,8 @@ static inline int check_data_rlimit(unsigned long rlim,
extern int mm_take_all_locks(struct mm_struct *mm);
extern void mm_drop_all_locks(struct mm_struct *mm);
extern void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file);
extern int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file);
extern int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file);
extern struct file *get_mm_exe_file(struct mm_struct *mm);
extern struct file *get_task_exe_file(struct task_struct *task);
......
......@@ -32,7 +32,8 @@
* The historical set of flags that all mmap implementations implicitly
* support when a ->mmap_validate() op is not provided in file_operations.
*
* MAP_EXECUTABLE is completely ignored throughout the kernel.
* MAP_EXECUTABLE and MAP_DENYWRITE are completely ignored throughout the
* kernel.
*/
#define LEGACY_MAP_MASK (MAP_SHARED \
| MAP_PRIVATE \
......@@ -153,7 +154,6 @@ static inline unsigned long
calc_vm_flag_bits(unsigned long flags)
{
return _calc_vm_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN ) |
_calc_vm_trans(flags, MAP_DENYWRITE, VM_DENYWRITE ) |
_calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ) |
_calc_vm_trans(flags, MAP_SYNC, VM_SYNC ) |
arch_calc_vm_flag_bits(flags);
......
......@@ -165,7 +165,6 @@ IF_HAVE_PG_SKIP_KASAN_POISON(PG_skip_kasan_poison, "skip_kasan_poison")
{VM_UFFD_MISSING, "uffd_missing" }, \
IF_HAVE_UFFD_MINOR(VM_UFFD_MINOR, "uffd_minor" ) \
{VM_PFNMAP, "pfnmap" }, \
{VM_DENYWRITE, "denywrite" }, \
{VM_UFFD_WP, "uffd_wp" }, \
{VM_LOCKED, "locked" }, \
{VM_IO, "io" }, \
......
......@@ -8320,8 +8320,6 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
else
flags = MAP_PRIVATE;
if (vma->vm_flags & VM_DENYWRITE)
flags |= MAP_DENYWRITE;
if (vma->vm_flags & VM_LOCKED)
flags |= MAP_LOCKED;
if (is_vm_hugetlb_page(vma))
......
......@@ -471,6 +471,20 @@ void free_task(struct task_struct *tsk)
}
EXPORT_SYMBOL(free_task);
static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
{
struct file *exe_file;
exe_file = get_mm_exe_file(oldmm);
RCU_INIT_POINTER(mm->exe_file, exe_file);
/*
* We depend on the oldmm having properly denied write access to the
* exe_file already.
*/
if (exe_file && deny_write_access(exe_file))
pr_warn_once("deny_write_access() failed in %s\n", __func__);
}
#ifdef CONFIG_MMU
static __latent_entropy int dup_mmap(struct mm_struct *mm,
struct mm_struct *oldmm)
......@@ -494,7 +508,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
/* No ordering required: file already has been exposed. */
RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
dup_mm_exe_file(mm, oldmm);
mm->total_vm = oldmm->total_vm;
mm->data_vm = oldmm->data_vm;
......@@ -557,12 +571,9 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
file = tmp->vm_file;
if (file) {
struct inode *inode = file_inode(file);
struct address_space *mapping = file->f_mapping;
get_file(file);
if (tmp->vm_flags & VM_DENYWRITE)
put_write_access(inode);
i_mmap_lock_write(mapping);
if (tmp->vm_flags & VM_SHARED)
mapping_allow_writable(mapping);
......@@ -640,7 +651,7 @@ static inline void mm_free_pgd(struct mm_struct *mm)
static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
{
mmap_write_lock(oldmm);
RCU_INIT_POINTER(mm->exe_file, get_mm_exe_file(oldmm));
dup_mm_exe_file(mm, oldmm);
mmap_write_unlock(oldmm);
return 0;
}
......@@ -1150,11 +1161,11 @@ void mmput_async(struct mm_struct *mm)
*
* Main users are mmput() and sys_execve(). Callers prevent concurrent
* invocations: in mmput() nobody alive left, in execve task is single
* threaded. sys_prctl(PR_SET_MM_MAP/EXE_FILE) also needs to set the
* mm->exe_file, but does so without using set_mm_exe_file() in order
* to avoid the need for any locks.
* threaded.
*
* Can only fail if new_exe_file != NULL.
*/
void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
{
struct file *old_exe_file;
......@@ -1165,11 +1176,73 @@ void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
*/
old_exe_file = rcu_dereference_raw(mm->exe_file);
if (new_exe_file)
if (new_exe_file) {
/*
* We expect the caller (i.e., sys_execve) to already denied
* write access, so this is unlikely to fail.
*/
if (unlikely(deny_write_access(new_exe_file)))
return -EACCES;
get_file(new_exe_file);
}
rcu_assign_pointer(mm->exe_file, new_exe_file);
if (old_exe_file)
if (old_exe_file) {
allow_write_access(old_exe_file);
fput(old_exe_file);
}
return 0;
}
/**
* replace_mm_exe_file - replace a reference to the mm's executable file
*
* This changes mm's executable file (shown as symlink /proc/[pid]/exe),
* dealing with concurrent invocation and without grabbing the mmap lock in
* write mode.
*
* Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
*/
int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
{
struct vm_area_struct *vma;
struct file *old_exe_file;
int ret = 0;
/* Forbid mm->exe_file change if old file still mapped. */
old_exe_file = get_mm_exe_file(mm);
if (old_exe_file) {
mmap_read_lock(mm);
for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) {
if (!vma->vm_file)
continue;
if (path_equal(&vma->vm_file->f_path,
&old_exe_file->f_path))
ret = -EBUSY;
}
mmap_read_unlock(mm);
fput(old_exe_file);
if (ret)
return ret;
}
/* set the new file, lockless */
ret = deny_write_access(new_exe_file);
if (ret)
return -EACCES;
get_file(new_exe_file);
old_exe_file = xchg(&mm->exe_file, new_exe_file);
if (old_exe_file) {
/*
* Don't race with dup_mmap() getting the file and disallowing
* write access while someone might open the file writable.
*/
mmap_read_lock(mm);
allow_write_access(old_exe_file);
fput(old_exe_file);
mmap_read_unlock(mm);
}
return 0;
}
/**
......
......@@ -1847,7 +1847,6 @@ SYSCALL_DEFINE1(umask, int, mask)
static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
{
struct fd exe;
struct file *old_exe, *exe_file;
struct inode *inode;
int err;
......@@ -1870,40 +1869,10 @@ static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
if (err)
goto exit;
/*
* Forbid mm->exe_file change if old file still mapped.
*/
exe_file = get_mm_exe_file(mm);
err = -EBUSY;
if (exe_file) {
struct vm_area_struct *vma;
mmap_read_lock(mm);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
if (!vma->vm_file)
continue;
if (path_equal(&vma->vm_file->f_path,
&exe_file->f_path))
goto exit_err;
}
mmap_read_unlock(mm);
fput(exe_file);
}
err = 0;
/* set the new file, lockless */
get_file(exe.file);
old_exe = xchg(&mm->exe_file, exe.file);
if (old_exe)
fput(old_exe);
err = replace_mm_exe_file(mm, exe.file);
exit:
fdput(exe);
return err;
exit_err:
mmap_read_unlock(mm);
fput(exe_file);
goto exit;
}
/*
......
......@@ -675,9 +675,8 @@ flags(void)
"uptodate|dirty|lru|active|swapbacked",
cmp_buffer);
flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC
| VM_DENYWRITE;
test("read|exec|mayread|maywrite|mayexec|denywrite", "%pGv", &flags);
flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
test("read|exec|mayread|maywrite|mayexec", "%pGv", &flags);
gfp = GFP_TRANSHUGE;
test("GFP_TRANSHUGE", "%pGg", &gfp);
......
......@@ -148,8 +148,6 @@ void vma_set_page_prot(struct vm_area_struct *vma)
static void __remove_shared_vm_struct(struct vm_area_struct *vma,
struct file *file, struct address_space *mapping)
{
if (vma->vm_flags & VM_DENYWRITE)
allow_write_access(file);
if (vma->vm_flags & VM_SHARED)
mapping_unmap_writable(mapping);
......@@ -667,8 +665,6 @@ static void __vma_link_file(struct vm_area_struct *vma)
if (file) {
struct address_space *mapping = file->f_mapping;
if (vma->vm_flags & VM_DENYWRITE)
put_write_access(file_inode(file));
if (vma->vm_flags & VM_SHARED)
mapping_allow_writable(mapping);
......@@ -1625,8 +1621,6 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
return PTR_ERR(file);
}
flags &= ~MAP_DENYWRITE;
retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
out_fput:
if (file)
......@@ -1783,22 +1777,12 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
vma->vm_pgoff = pgoff;
if (file) {
if (vm_flags & VM_DENYWRITE) {
error = deny_write_access(file);
if (error)
goto free_vma;
}
if (vm_flags & VM_SHARED) {
error = mapping_map_writable(file->f_mapping);
if (error)
goto allow_write_and_free_vma;
goto free_vma;
}
/* ->mmap() can change vma->vm_file, but must guarantee that
* vma_link() below can deny write-access if VM_DENYWRITE is set
* and map writably if VM_SHARED is set. This usually means the
* new file must not have been exposed to user-space, yet.
*/
vma->vm_file = get_file(file);
error = call_mmap(file, vma);
if (error)
......@@ -1855,13 +1839,9 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
vma_link(mm, vma, prev, rb_link, rb_parent);
/* Once vma denies write, undo our temporary denial count */
if (file) {
unmap_writable:
if (vm_flags & VM_SHARED)
mapping_unmap_writable(file->f_mapping);
if (vm_flags & VM_DENYWRITE)
allow_write_access(file);
}
if (file && vm_flags & VM_SHARED)
mapping_unmap_writable(file->f_mapping);
file = vma->vm_file;
out:
perf_event_mmap(vma);
......@@ -1901,9 +1881,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
charged = 0;
if (vm_flags & VM_SHARED)
mapping_unmap_writable(file->f_mapping);
allow_write_and_free_vma:
if (vm_flags & VM_DENYWRITE)
allow_write_access(file);
free_vma:
vm_area_free(vma);
unacct_error:
......
......@@ -1293,8 +1293,6 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
goto out;
}
flags &= ~MAP_DENYWRITE;
retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
if (file)
......
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