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Message-ID: <20091117235401.30900.70697.stgit@dhcp-100-2-132.bos.redhat.com>
Date: Tue, 17 Nov 2009 18:54:01 -0500
From: Masami Hiramatsu <mhiramat@...hat.com>
To: Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>
Cc: systemtap <systemtap@...rces.redhat.com>,
DLE <dle-develop@...ts.sourceforge.net>,
Masami Hiramatsu <mhiramat@...hat.com>,
Roland McGrath <roland@...hat.com>,
Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Oleg Nesterov <oleg@...hat.com>, Ingo Molnar <mingo@...e.hu>
Subject: [PATCH -tip 2/2] Pass mm->flags as a coredump parameter for
consistency
Pass mm->flags as a coredump parameter for consistency.
---
1787 if (mm->core_state || !get_dumpable(mm)) { <- (1)
1788 up_write(&mm->mmap_sem);
1789 put_cred(cred);
1790 goto fail;
1791 }
1792
[...]
1798 if (get_dumpable(mm) == 2) { /* Setuid core dump mode */ <-(2)
1799 flag = O_EXCL; /* Stop rewrite attacks */
1800 cred->fsuid = 0; /* Dump root private */
1801 }
---
Since dumpable bits are not protected by lock, there is a
chance to change these bits between (1) and (2).
To solve this issue, this patch copies mm->flags to
coredump_params.mm_flags at the beginning of do_coredump() and uses it instead of get_dumpable() while dumping core.
This copy is also passed to binfmt->core_dump, since
elf*_core_dump() uses dump_filter bits in mm->flags.
Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Roland McGrath <roland@...hat.com>
Cc: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Ingo Molnar <mingo@...e.hu>
---
fs/binfmt_elf.c | 12 ++----------
fs/binfmt_elf_fdpic.c | 12 ++----------
fs/exec.c | 20 ++++++++++++++++----
include/linux/binfmts.h | 1 +
4 files changed, 21 insertions(+), 24 deletions(-)
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 5e27303..2f76489 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1911,7 +1911,6 @@ static int elf_core_dump(struct coredump_params *cprm)
struct vm_area_struct *vma, *gate_vma;
struct elfhdr *elf = NULL;
loff_t offset = 0, dataoff, foffset;
- unsigned long mm_flags;
struct elf_note_info info;
/*
@@ -1982,13 +1981,6 @@ static int elf_core_dump(struct coredump_params *cprm)
dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);
- /*
- * We must use the same mm->flags while dumping core to avoid
- * inconsistency between the program headers and bodies, otherwise an
- * unusable core file can be generated.
- */
- mm_flags = current->mm->flags;
-
/* Write program headers for segments dump */
for (vma = first_vma(current, gate_vma); vma != NULL;
vma = next_vma(vma, gate_vma)) {
@@ -1998,7 +1990,7 @@ static int elf_core_dump(struct coredump_params *cprm)
phdr.p_offset = offset;
phdr.p_vaddr = vma->vm_start;
phdr.p_paddr = 0;
- phdr.p_filesz = vma_dump_size(vma, mm_flags);
+ phdr.p_filesz = vma_dump_size(vma, cprm->mm_flags);
phdr.p_memsz = vma->vm_end - vma->vm_start;
offset += phdr.p_filesz;
phdr.p_flags = vma->vm_flags & VM_READ ? PF_R : 0;
@@ -2034,7 +2026,7 @@ static int elf_core_dump(struct coredump_params *cprm)
unsigned long addr;
unsigned long end;
- end = vma->vm_start + vma_dump_size(vma, mm_flags);
+ end = vma->vm_start + vma_dump_size(vma, cprm->mm_flags);
for (addr = vma->vm_start; addr < end; addr += PAGE_SIZE) {
struct page *page;
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index e65ab9d..28af3e9 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -1604,7 +1604,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
#endif
int thread_status_size = 0;
elf_addr_t *auxv;
- unsigned long mm_flags;
/*
* We no longer stop all VM operations.
@@ -1735,13 +1734,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
/* Page-align dumped data */
dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);
- /*
- * We must use the same mm->flags while dumping core to avoid
- * inconsistency between the program headers and bodies, otherwise an
- * unusable core file can be generated.
- */
- mm_flags = current->mm->flags;
-
/* write program headers for segments dump */
for (vma = current->mm->mmap; vma; vma = vma->vm_next) {
struct elf_phdr phdr;
@@ -1753,7 +1745,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
phdr.p_offset = offset;
phdr.p_vaddr = vma->vm_start;
phdr.p_paddr = 0;
- phdr.p_filesz = maydump(vma, mm_flags) ? sz : 0;
+ phdr.p_filesz = maydump(vma, cprm->mm_flags) ? sz : 0;
phdr.p_memsz = sz;
offset += phdr.p_filesz;
phdr.p_flags = vma->vm_flags & VM_READ ? PF_R : 0;
@@ -1789,7 +1781,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
goto end_coredump;
if (elf_fdpic_dump_segments(cprm->file, &size, &cprm->limit,
- mm_flags) < 0)
+ cprm->mm_flags) < 0)
goto end_coredump;
#ifdef ELF_CORE_WRITE_EXTRA_DATA
diff --git a/fs/exec.c b/fs/exec.c
index 5daf7d5..2ec6973 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1718,14 +1718,19 @@ void set_dumpable(struct mm_struct *mm, int value)
}
}
-int get_dumpable(struct mm_struct *mm)
+static int __get_dumpable(unsigned long mm_flags)
{
int ret;
- ret = mm->flags & 0x3;
+ ret = mm_flags & MMF_DUMPABLE_MASK;
return (ret >= 2) ? 2 : ret;
}
+int get_dumpable(struct mm_struct *mm)
+{
+ return __get_dumpable(mm->flags);
+}
+
static void wait_for_dump_helpers(struct file *file)
{
struct pipe_inode_info *pipe;
@@ -1769,6 +1774,12 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
.signr = signr,
.regs = regs,
.limit = current->signal->rlim[RLIMIT_CORE].rlim_cur,
+ /*
+ * We must use the same mm->flags while dumping core to avoid
+ * inconsistency of bit flags, since this flag is not protected
+ * by any locks.
+ */
+ .mm_flags = mm->flags,
};
audit_core_dumps(signr);
@@ -1787,7 +1798,7 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
/*
* If another thread got here first, or we are not dumpable, bail out.
*/
- if (mm->core_state || !get_dumpable(mm)) {
+ if (mm->core_state || !__get_dumpable(cprm.mm_flags)) {
up_write(&mm->mmap_sem);
put_cred(cred);
goto fail;
@@ -1798,7 +1809,8 @@ void 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 (get_dumpable(mm) == 2) { /* Setuid core dump mode */
+ if (__get_dumpable(cprm.mm_flags) == 2) {
+ /* Setuid core dump mode */
flag = O_EXCL; /* Stop rewrite attacks */
cred->fsuid = 0; /* Dump root private */
}
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index cd4349b..99e529b 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -74,6 +74,7 @@ struct coredump_params {
struct pt_regs *regs;
struct file *file;
unsigned long limit;
+ unsigned long mm_flags;
};
/*
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division
e-mail: mhiramat@...hat.com
--
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