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coredump masking: reimplementation of dumpable using two flags

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This patch changes mm_struct.dumpable to a pair of bit flags.

set_dumpable() converts three-value dumpable to two flags and stores it into
lower two bits of mm_struct.flags instead of mm_struct.dumpable.
get_dumpable() behaves in the opposite way.

[akpm@linux-foundation.org: export set_dumpable]
Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kawai, Hidehiro 2007-07-19 01:48:27 -07:00 committed by Linus Torvalds
parent 76fdbb25f9
commit 6c5d523826
8 changed files with 82 additions and 25 deletions
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62
fs/exec.c
View file

@ -1058,9 +1058,9 @@ int flush_old_exec(struct linux_binprm * bprm)
current->sas_ss_sp = current->sas_ss_size = 0;
if (current->euid == current->uid && current->egid == current->gid)
current->mm->dumpable = 1;
set_dumpable(current->mm, 1);
else
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
name = bprm->filename;
@ -1088,7 +1088,7 @@ int flush_old_exec(struct linux_binprm * bprm)
file_permission(bprm->file, MAY_READ) ||
(bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
suid_keys(current);
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
}
/* An exec changes our domain. We are no longer part of the thread
@ -1665,6 +1665,56 @@ fail:
return core_waiters;
}
/*
* set_dumpable converts traditional three-value dumpable to two flags and
* stores them into mm->flags. It modifies lower two bits of mm->flags, but
* these bits are not changed atomically. So get_dumpable can observe the
* intermediate state. To avoid doing unexpected behavior, get get_dumpable
* return either old dumpable or new one by paying attention to the order of
* modifying the bits.
*
* dumpable | mm->flags (binary)
* old new | initial interim final
* ---------+-----------------------
* 0 1 | 00 01 01
* 0 2 | 00 10(*) 11
* 1 0 | 01 00 00
* 1 2 | 01 11 11
* 2 0 | 11 10(*) 00
* 2 1 | 11 11 01
*
* (*) get_dumpable regards interim value of 10 as 11.
*/
void set_dumpable(struct mm_struct *mm, int value)
{
switch (value) {
case 0:
clear_bit(MMF_DUMPABLE, &mm->flags);
smp_wmb();
clear_bit(MMF_DUMP_SECURELY, &mm->flags);
break;
case 1:
set_bit(MMF_DUMPABLE, &mm->flags);
smp_wmb();
clear_bit(MMF_DUMP_SECURELY, &mm->flags);
break;
case 2:
set_bit(MMF_DUMP_SECURELY, &mm->flags);
smp_wmb();
set_bit(MMF_DUMPABLE, &mm->flags);
break;
}
}
EXPORT_SYMBOL_GPL(set_dumpable);
int get_dumpable(struct mm_struct *mm)
{
int ret;
ret = mm->flags & 0x3;
return (ret >= 2) ? 2 : ret;
}
int do_coredump(long signr, int exit_code, struct pt_regs * regs)
{
char corename[CORENAME_MAX_SIZE + 1];
@ -1683,7 +1733,7 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
if (!binfmt || !binfmt->core_dump)
goto fail;
down_write(&mm->mmap_sem);
if (!mm->dumpable) {
if (!get_dumpable(mm)) {
up_write(&mm->mmap_sem);
goto fail;
}
@ -1693,11 +1743,11 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
* process nor do we know its entire history. We only know it
* was tainted so we dump it as root in mode 2.
*/
if (mm->dumpable == 2) { /* Setuid core dump mode */
if (get_dumpable(mm) == 2) { /* Setuid core dump mode */
flag = O_EXCL; /* Stop rewrite attacks */
current->fsuid = 0; /* Dump root private */
}
mm->dumpable = 0;
set_dumpable(mm, 0);
retval = coredump_wait(exit_code);
if (retval < 0)

2
fs/proc/base.c
View file

@ -1014,7 +1014,7 @@ static int task_dumpable(struct task_struct *task)
task_lock(task);
mm = task->mm;
if (mm)
dumpable = mm->dumpable;
dumpable = get_dumpable(mm);
task_unlock(task);
if(dumpable == 1)
return 1;

4
include/asm-ia64/processor.h
View file

@ -295,9 +295,9 @@ struct thread_struct {
regs->ar_bspstore = current->thread.rbs_bot; \
regs->ar_fpsr = FPSR_DEFAULT; \
regs->loadrs = 0; \
regs->r8 = current->mm->dumpable; /* set "don't zap registers" flag */ \
regs->r8 = get_dumpable(current->mm); /* set "don't zap registers" flag */ \
regs->r12 = new_sp - 16; /* allocate 16 byte scratch area */ \
if (unlikely(!current->mm->dumpable)) { \
if (unlikely(!get_dumpable(current->mm))) { \
/* \
* Zap scratch regs to avoid leaking bits between processes with different \
* uid/privileges. \

9
include/linux/sched.h
View file

@ -345,6 +345,13 @@ typedef unsigned long mm_counter_t;
(mm)->hiwater_vm = (mm)->total_vm; \
} while (0)
extern void set_dumpable(struct mm_struct *mm, int value);
extern int get_dumpable(struct mm_struct *mm);
/* mm flags */
#define MMF_DUMPABLE 0 /* core dump is permitted */
#define MMF_DUMP_SECURELY 1 /* core file is readable only by root */
struct mm_struct {
struct vm_area_struct * mmap; /* list of VMAs */
struct rb_root mm_rb;
@ -402,7 +409,7 @@ struct mm_struct {
unsigned int token_priority;
unsigned int last_interval;
unsigned char dumpable:2;
unsigned long flags; /* Must use atomic bitops to access the bits */
/* coredumping support */
int core_waiters;

2
kernel/ptrace.c
View file

@ -142,7 +142,7 @@ static int may_attach(struct task_struct *task)
return -EPERM;
smp_rmb();
if (task->mm)
dumpable = task->mm->dumpable;
dumpable = get_dumpable(task->mm);
if (!dumpable && !capable(CAP_SYS_PTRACE))
return -EPERM;

24
kernel/sys.c
View file

@ -1036,7 +1036,7 @@ asmlinkage long sys_setregid(gid_t rgid, gid_t egid)
return -EPERM;
}
if (new_egid != old_egid) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
smp_wmb();
}
if (rgid != (gid_t) -1 ||
@ -1066,13 +1066,13 @@ asmlinkage long sys_setgid(gid_t gid)
if (capable(CAP_SETGID)) {
if (old_egid != gid) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
smp_wmb();
}
current->gid = current->egid = current->sgid = current->fsgid = gid;
} else if ((gid == current->gid) || (gid == current->sgid)) {
if (old_egid != gid) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
smp_wmb();
}
current->egid = current->fsgid = gid;
@ -1103,7 +1103,7 @@ static int set_user(uid_t new_ruid, int dumpclear)
switch_uid(new_user);
if (dumpclear) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
smp_wmb();
}
current->uid = new_ruid;
@ -1159,7 +1159,7 @@ asmlinkage long sys_setreuid(uid_t ruid, uid_t euid)
return -EAGAIN;
if (new_euid != old_euid) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
smp_wmb();
}
current->fsuid = current->euid = new_euid;
@ -1209,7 +1209,7 @@ asmlinkage long sys_setuid(uid_t uid)
return -EPERM;
if (old_euid != uid) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
smp_wmb();
}
current->fsuid = current->euid = uid;
@ -1254,7 +1254,7 @@ asmlinkage long sys_setresuid(uid_t ruid, uid_t euid, uid_t suid)
}
if (euid != (uid_t) -1) {
if (euid != current->euid) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
smp_wmb();
}
current->euid = euid;
@ -1304,7 +1304,7 @@ asmlinkage long sys_setresgid(gid_t rgid, gid_t egid, gid_t sgid)
}
if (egid != (gid_t) -1) {
if (egid != current->egid) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
smp_wmb();
}
current->egid = egid;
@ -1350,7 +1350,7 @@ asmlinkage long sys_setfsuid(uid_t uid)
uid == current->suid || uid == current->fsuid ||
capable(CAP_SETUID)) {
if (uid != old_fsuid) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
smp_wmb();
}
current->fsuid = uid;
@ -1379,7 +1379,7 @@ asmlinkage long sys_setfsgid(gid_t gid)
gid == current->sgid || gid == current->fsgid ||
capable(CAP_SETGID)) {
if (gid != old_fsgid) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
smp_wmb();
}
current->fsgid = gid;
@ -2176,14 +2176,14 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
error = put_user(current->pdeath_signal, (int __user *)arg2);
break;
case PR_GET_DUMPABLE:
error = current->mm->dumpable;
error = get_dumpable(current->mm);
break;
case PR_SET_DUMPABLE:
if (arg2 < 0 || arg2 > 1) {
error = -EINVAL;
break;
}
current->mm->dumpable = arg2;
set_dumpable(current->mm, arg2);
break;
case PR_SET_UNALIGN:

2
security/commoncap.c
View file

@ -148,7 +148,7 @@ void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
!cap_issubset (new_permitted, current->cap_permitted)) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
if (!capable(CAP_SETUID)) {

2
security/dummy.c
View file

@ -130,7 +130,7 @@ static void dummy_bprm_free_security (struct linux_binprm *bprm)
static void dummy_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
{
if (bprm->e_uid != current->uid || bprm->e_gid != current->gid) {
current->mm->dumpable = suid_dumpable;
set_dumpable(current->mm, suid_dumpable);
if ((unsafe & ~LSM_UNSAFE_PTRACE_CAP) && !capable(CAP_SETUID)) {
bprm->e_uid = current->uid;