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Message-ID: <4656DF5D.5090909@hitachi.com>
Date: Fri, 25 May 2007 22:06:37 +0900
From: "Kawai, Hidehiro" <hidehiro.kawai.ez@...achi.com>
To: linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Cc: dhowells@...hat.com, holt@....com, alan@...rguk.ukuu.org.uk,
masami.hiramatsu.pt@...achi.com, yumiko.sugita.yf@...achi.com,
soshima@...hat.com, haoki@...hat.com
Subject: [PATCH 2/7] reimplementation of dumpable using two flags
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.
Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
---
fs/exec.c | 61 +++++++++++++++++++++++++++++----
fs/proc/base.c | 2 -
include/asm-ia64/processor.h | 4 +-
include/linux/sched.h | 9 ++++
kernel/ptrace.c | 2 -
kernel/sys.c | 24 ++++++------
security/commoncap.c | 2 -
security/dummy.c | 2 -
8 files changed, 81 insertions(+), 25 deletions(-)
Index: linux-2.6.22-rc2-mm1/fs/exec.c
===================================================================
--- linux-2.6.22-rc2-mm1.orig/fs/exec.c
+++ linux-2.6.22-rc2-mm1/fs/exec.c
@@ -864,9 +864,9 @@ int flush_old_exec(struct linux_binprm *
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;
@@ -894,7 +894,7 @@ int flush_old_exec(struct linux_binprm *
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
@@ -1484,6 +1484,55 @@ 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;
+ }
+}
+
+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];
@@ -1502,7 +1551,7 @@ int do_coredump(long signr, int exit_cod
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;
}
@@ -1512,11 +1561,11 @@ int do_coredump(long signr, int exit_cod
* 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)
Index: linux-2.6.22-rc2-mm1/include/linux/sched.h
===================================================================
--- linux-2.6.22-rc2-mm1.orig/include/linux/sched.h
+++ linux-2.6.22-rc2-mm1/include/linux/sched.h
@@ -324,6 +324,13 @@ 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;
@@ -381,7 +388,7 @@ 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;
Index: linux-2.6.22-rc2-mm1/fs/proc/base.c
===================================================================
--- linux-2.6.22-rc2-mm1.orig/fs/proc/base.c
+++ linux-2.6.22-rc2-mm1/fs/proc/base.c
@@ -1037,7 +1037,7 @@ static int task_dumpable(struct task_str
task_lock(task);
mm = task->mm;
if (mm)
- dumpable = mm->dumpable;
+ dumpable = get_dumpable(mm);
task_unlock(task);
if(dumpable == 1)
return 1;
Index: linux-2.6.22-rc2-mm1/include/asm-ia64/processor.h
===================================================================
--- linux-2.6.22-rc2-mm1.orig/include/asm-ia64/processor.h
+++ linux-2.6.22-rc2-mm1/include/asm-ia64/processor.h
@@ -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. \
Index: linux-2.6.22-rc2-mm1/kernel/ptrace.c
===================================================================
--- linux-2.6.22-rc2-mm1.orig/kernel/ptrace.c
+++ linux-2.6.22-rc2-mm1/kernel/ptrace.c
@@ -142,7 +142,7 @@ static int may_attach(struct task_struct
return -EPERM;
smp_rmb();
if (task->mm)
- dumpable = task->mm->dumpable;
+ dumpable = get_dumpable(task->mm);
if (!dumpable && !capable(CAP_SYS_PTRACE))
return -EPERM;
Index: linux-2.6.22-rc2-mm1/kernel/sys.c
===================================================================
--- linux-2.6.22-rc2-mm1.orig/kernel/sys.c
+++ linux-2.6.22-rc2-mm1/kernel/sys.c
@@ -1025,7 +1025,7 @@ asmlinkage long sys_setregid(gid_t rgid,
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 ||
@@ -1055,13 +1055,13 @@ 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;
@@ -1092,7 +1092,7 @@ static int set_user(uid_t new_ruid, int
switch_uid(new_user);
if (dumpclear) {
- current->mm->dumpable = suid_dumpable;
+ set_dumpable(current->mm, suid_dumpable);
smp_wmb();
}
current->uid = new_ruid;
@@ -1148,7 +1148,7 @@ asmlinkage long sys_setreuid(uid_t ruid,
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;
@@ -1198,7 +1198,7 @@ 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;
@@ -1243,7 +1243,7 @@ asmlinkage long sys_setresuid(uid_t ruid
}
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;
@@ -1293,7 +1293,7 @@ asmlinkage long sys_setresgid(gid_t rgid
}
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;
@@ -1339,7 +1339,7 @@ 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;
@@ -1368,7 +1368,7 @@ 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;
@@ -2165,14 +2165,14 @@ asmlinkage long sys_prctl(int option, un
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:
Index: linux-2.6.22-rc2-mm1/security/commoncap.c
===================================================================
--- linux-2.6.22-rc2-mm1.orig/security/commoncap.c
+++ linux-2.6.22-rc2-mm1/security/commoncap.c
@@ -241,7 +241,7 @@ void cap_bprm_apply_creds (struct linux_
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)) {
Index: linux-2.6.22-rc2-mm1/security/dummy.c
===================================================================
--- linux-2.6.22-rc2-mm1.orig/security/dummy.c
+++ linux-2.6.22-rc2-mm1/security/dummy.c
@@ -130,7 +130,7 @@ static void dummy_bprm_free_security (st
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;
-
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