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SubjectRe: Cross Memory Attach v3 (includes updated patch based on v4)
On Thu, 21 Jul 2011 15:09:08 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Tue, 19 Jul 2011 00:35:37 +0930
> Christopher Yeoh <cyeoh@au1.ibm.com> wrote:
>
> > +
> > +static ssize_t process_vm_rw(pid_t pid, const struct iovec *lvec,
> > + unsigned long liovcnt,
> > + const struct iovec *rvec,
> > + unsigned long riovcnt,
> > + unsigned long flags, int vm_write)
> > +{
> > + struct task_struct *task;
> > + struct page **process_pages = NULL;
> > + struct mm_struct *mm;
> > + unsigned long i;
> > + ssize_t rc;
> > + ssize_t bytes_copied;
> > + unsigned long nr_pages = 0;
> > + unsigned long nr_pages_iov;
> > + unsigned long iov_l_curr_idx = 0;
> > + size_t iov_l_curr_offset = 0;
> > + ssize_t iov_len;
> > +
> > + /*
> > + * Work out how many pages of struct pages we're going to
> > need
> > + * when eventually calling get_user_pages
> > + */
> > + for (i = 0; i < riovcnt; i++) {
> > + iov_len = rvec[i].iov_len;
> > + if (iov_len > 0) {
> > + nr_pages_iov = ((unsigned
> > long)rvec[i].iov_base
> > + + iov_len)
> > + / PAGE_SIZE - (unsigned
> > long)rvec[i].iov_base
> > + / PAGE_SIZE + 1;
> > + nr_pages = max(nr_pages, nr_pages_iov);
> > + }
> > + }
> > +
> > + if (nr_pages == 0)
> > + return 0;
> > +
> > + /* For reliability don't try to kmalloc more than 2 pages
> > worth */
> > + process_pages = kmalloc(min_t(size_t,
> > PVM_MAX_KMALLOC_PAGES,
> > + sizeof(struct pages
> > *)*nr_pages),
> > + GFP_KERNEL);
>
> You might get some speed benefit by optimising for the small copies
> here. Define a local on-stack array of N page*'s and point
> process_pages at that if the number of pages is <= N. Saves a
> malloc/free and is more cache-friendly. But only if the result is
> measurable!

I have done some benchmarking on this, and it gains about 5-7% on a
microbenchmark with 4kb size copies and about a 1% gain with a more
realistic (but modified for smaller copies) hpcc benchmark. The
performance gain disappears into the noise by about 64kb sized copies.
No measurable overhead for larger copies. So I think its worth including

Included below is the patch (based on v4) - for ease of review the first diff
is just against the latest version of CMA which has been posted here previously.
The second is the entire CMA patch.

Signed-off-by: Chris Yeoh <cyeoh@au1.ibm.com>
---
process_vm_access.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index 5ac8abc..e920aa3 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -221,6 +221,10 @@ static int process_vm_rw_single_vec(unsigned long addr,
return rc;
}

+/* Maximum number of entries for process pages array
+ which lives on stack */
+#define PVM_MAX_PP_ARRAY_COUNT 16
+
/**
* process_vm_rw_core - core of reading/writing pages from task specified
* @pid: PID of process to read/write from/to
@@ -241,7 +245,8 @@ static ssize_t process_vm_rw_core(pid_t pid, const struct iovec *lvec,
unsigned long flags, int vm_write)
{
struct task_struct *task;
- struct page **process_pages = NULL;
+ struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
+ struct page **process_pages = pp_stack;
struct mm_struct *mm;
unsigned long i;
ssize_t rc = 0;
@@ -271,13 +276,16 @@ static ssize_t process_vm_rw_core(pid_t pid, const struct iovec *lvec,
if (nr_pages == 0)
return 0;

- /* For reliability don't try to kmalloc more than 2 pages worth */
- process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
- sizeof(struct pages *)*nr_pages),
- GFP_KERNEL);
+ if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
+ /* For reliability don't try to kmalloc more than
+ 2 pages worth */
+ process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
+ sizeof(struct pages *)*nr_pages),
+ GFP_KERNEL);

- if (!process_pages)
- return -ENOMEM;
+ if (!process_pages)
+ return -ENOMEM;
+ }

/* Get process information */
rcu_read_lock();
@@ -331,7 +339,8 @@ put_task_struct:
put_task_struct(task);

free_proc_pages:
- kfree(process_pages);
+ if (process_pages != pp_stack)
+ kfree(process_pages);
return rc;
}

Signed-off-by: Chris Yeoh <cyeoh@au1.ibm.com>
---
arch/powerpc/include/asm/systbl.h | 2
arch/powerpc/include/asm/unistd.h | 4
arch/x86/ia32/ia32entry.S | 2
arch/x86/include/asm/unistd_32.h | 4
arch/x86/include/asm/unistd_64.h | 4
arch/x86/kernel/syscall_table_32.S | 2
fs/aio.c | 4
fs/compat.c | 7
fs/read_write.c | 8
include/linux/compat.h | 3
include/linux/fs.h | 7
include/linux/syscalls.h | 13
kernel/sys_ni.c | 4
mm/Makefile | 3
mm/process_vm_access.c | 496 +++++++++++++++++++++++++++++++++++++
security/keys/compat.c | 2
security/keys/keyctl.c | 2
17 files changed, 550 insertions(+), 17 deletions(-)
diff --git a/arch/powerpc/include/asm/systbl.h b/arch/powerpc/include/asm/systbl.h
index f6736b7..525db4b 100644
--- a/arch/powerpc/include/asm/systbl.h
+++ b/arch/powerpc/include/asm/systbl.h
@@ -354,3 +354,5 @@ COMPAT_SYS_SPU(clock_adjtime)
SYSCALL_SPU(syncfs)
COMPAT_SYS_SPU(sendmmsg)
SYSCALL_SPU(setns)
+COMPAT_SYS(process_vm_readv)
+COMPAT_SYS(process_vm_writev)
diff --git a/arch/powerpc/include/asm/unistd.h b/arch/powerpc/include/asm/unistd.h
index b8b3f59..d3d1b5e 100644
--- a/arch/powerpc/include/asm/unistd.h
+++ b/arch/powerpc/include/asm/unistd.h
@@ -373,10 +373,12 @@
#define __NR_syncfs 348
#define __NR_sendmmsg 349
#define __NR_setns 350
+#define __NR_process_vm_readv 351
+#define __NR_process_vm_writev 352

#ifdef __KERNEL__

-#define __NR_syscalls 351
+#define __NR_syscalls 353

#define __NR__exit __NR_exit
#define NR_syscalls __NR_syscalls
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index c1870dd..cde849f 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -850,4 +850,6 @@ ia32_sys_call_table:
.quad sys_syncfs
.quad compat_sys_sendmmsg /* 345 */
.quad sys_setns
+ .quad compat_sys_process_vm_readv
+ .quad compat_sys_process_vm_writev
ia32_syscall_end:
diff --git a/arch/x86/include/asm/unistd_32.h b/arch/x86/include/asm/unistd_32.h
index 593485b..599c77d 100644
--- a/arch/x86/include/asm/unistd_32.h
+++ b/arch/x86/include/asm/unistd_32.h
@@ -352,10 +352,12 @@
#define __NR_syncfs 344
#define __NR_sendmmsg 345
#define __NR_setns 346
+#define __NR_process_vm_readv 347
+#define __NR_process_vm_writev 348

#ifdef __KERNEL__

-#define NR_syscalls 347
+#define NR_syscalls 349

#define __ARCH_WANT_IPC_PARSE_VERSION
#define __ARCH_WANT_OLD_READDIR
diff --git a/arch/x86/include/asm/unistd_64.h b/arch/x86/include/asm/unistd_64.h
index 705bf13..1f1d1ef 100644
--- a/arch/x86/include/asm/unistd_64.h
+++ b/arch/x86/include/asm/unistd_64.h
@@ -681,6 +681,10 @@ __SYSCALL(__NR_syncfs, sys_syncfs)
__SYSCALL(__NR_sendmmsg, sys_sendmmsg)
#define __NR_setns 308
__SYSCALL(__NR_setns, sys_setns)
+#define __NR_process_vm_readv 309
+__SYSCALL(__NR_process_vm_readv, sys_process_vm_readv)
+#define __NR_process_vm_writev 310
+__SYSCALL(__NR_process_vm_writev, sys_process_vm_writev)

#ifndef __NO_STUBS
#define __ARCH_WANT_OLD_READDIR
diff --git a/arch/x86/kernel/syscall_table_32.S b/arch/x86/kernel/syscall_table_32.S
index fbb0a04..ca0fe4d 100644
--- a/arch/x86/kernel/syscall_table_32.S
+++ b/arch/x86/kernel/syscall_table_32.S
@@ -346,3 +346,5 @@ ENTRY(sys_call_table)
.long sys_syncfs
.long sys_sendmmsg /* 345 */
.long sys_setns
+ .long sys_process_vm_readv
+ .long sys_process_vm_writev
diff --git a/fs/aio.c b/fs/aio.c
index e29ec48..632b235 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1387,13 +1387,13 @@ static ssize_t aio_setup_vectored_rw(int type, struct kiocb *kiocb, bool compat)
ret = compat_rw_copy_check_uvector(type,
(struct compat_iovec __user *)kiocb->ki_buf,
kiocb->ki_nbytes, 1, &kiocb->ki_inline_vec,
- &kiocb->ki_iovec);
+ &kiocb->ki_iovec, 1);
else
#endif
ret = rw_copy_check_uvector(type,
(struct iovec __user *)kiocb->ki_buf,
kiocb->ki_nbytes, 1, &kiocb->ki_inline_vec,
- &kiocb->ki_iovec);
+ &kiocb->ki_iovec, 1);
if (ret < 0)
goto out;

diff --git a/fs/compat.c b/fs/compat.c
index 0ea0083..ec53ccc 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -550,7 +550,7 @@ out:
ssize_t compat_rw_copy_check_uvector(int type,
const struct compat_iovec __user *uvector, unsigned long nr_segs,
unsigned long fast_segs, struct iovec *fast_pointer,
- struct iovec **ret_pointer)
+ struct iovec **ret_pointer, int check_access)
{
compat_ssize_t tot_len;
struct iovec *iov = *ret_pointer = fast_pointer;
@@ -597,7 +597,8 @@ ssize_t compat_rw_copy_check_uvector(int type,
}
if (len < 0) /* size_t not fitting in compat_ssize_t .. */
goto out;
- if (!access_ok(vrfy_dir(type), compat_ptr(buf), len)) {
+ if (check_access &&
+ !access_ok(vrfy_dir(type), compat_ptr(buf), len)) {
ret = -EFAULT;
goto out;
}
@@ -1111,7 +1112,7 @@ static ssize_t compat_do_readv_writev(int type, struct file *file,
goto out;

tot_len = compat_rw_copy_check_uvector(type, uvector, nr_segs,
- UIO_FASTIOV, iovstack, &iov);
+ UIO_FASTIOV, iovstack, &iov, 1);
if (tot_len == 0) {
ret = 0;
goto out;
diff --git a/fs/read_write.c b/fs/read_write.c
index 5520f8a..b905826 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -575,7 +575,8 @@ ssize_t do_loop_readv_writev(struct file *filp, struct iovec *iov,
ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
unsigned long nr_segs, unsigned long fast_segs,
struct iovec *fast_pointer,
- struct iovec **ret_pointer)
+ struct iovec **ret_pointer,
+ int check_access)
{
unsigned long seg;
ssize_t ret;
@@ -631,7 +632,8 @@ ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
ret = -EINVAL;
goto out;
}
- if (unlikely(!access_ok(vrfy_dir(type), buf, len))) {
+ if (check_access
+ && unlikely(!access_ok(vrfy_dir(type), buf, len))) {
ret = -EFAULT;
goto out;
}
@@ -663,7 +665,7 @@ static ssize_t do_readv_writev(int type, struct file *file,
}

ret = rw_copy_check_uvector(type, uvector, nr_segs,
- ARRAY_SIZE(iovstack), iovstack, &iov);
+ ARRAY_SIZE(iovstack), iovstack, &iov, 1);
if (ret <= 0)
goto out;

diff --git a/include/linux/compat.h b/include/linux/compat.h
index 846bb17..1cc917a 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -557,7 +557,8 @@ extern ssize_t compat_rw_copy_check_uvector(int type,
const struct compat_iovec __user *uvector,
unsigned long nr_segs,
unsigned long fast_segs, struct iovec *fast_pointer,
- struct iovec **ret_pointer);
+ struct iovec **ret_pointer,
+ int check_access);

extern void __user *compat_alloc_user_space(unsigned long len);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index b5b9792..d97ffab 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1608,9 +1608,10 @@ struct inode_operations {
struct seq_file;

ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
- unsigned long nr_segs, unsigned long fast_segs,
- struct iovec *fast_pointer,
- struct iovec **ret_pointer);
+ unsigned long nr_segs, unsigned long fast_segs,
+ struct iovec *fast_pointer,
+ struct iovec **ret_pointer,
+ int check_access);

extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 8c03b98..0dc0809 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -847,4 +847,17 @@ asmlinkage long sys_open_by_handle_at(int mountdirfd,
struct file_handle __user *handle,
int flags);
asmlinkage long sys_setns(int fd, int nstype);
+asmlinkage long sys_process_vm_readv(pid_t pid,
+ const struct iovec __user *lvec,
+ unsigned long liovcnt,
+ const struct iovec __user *rvec,
+ unsigned long riovcnt,
+ unsigned long flags);
+asmlinkage long sys_process_vm_writev(pid_t pid,
+ const struct iovec __user *lvec,
+ unsigned long liovcnt,
+ const struct iovec __user *rvec,
+ unsigned long riovcnt,
+ unsigned long flags);
+
#endif
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 62cbc88..7a34e9f 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -146,6 +146,10 @@ cond_syscall(sys_io_submit);
cond_syscall(sys_io_cancel);
cond_syscall(sys_io_getevents);
cond_syscall(sys_syslog);
+cond_syscall(sys_process_vm_readv);
+cond_syscall(sys_process_vm_writev);
+cond_syscall(compat_sys_process_vm_readv);
+cond_syscall(compat_sys_process_vm_writev);

/* arch-specific weak syscall entries */
cond_syscall(sys_pciconfig_read);
diff --git a/mm/Makefile b/mm/Makefile
index 836e416..50ec00e 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -5,7 +5,8 @@
mmu-y := nommu.o
mmu-$(CONFIG_MMU) := fremap.o highmem.o madvise.o memory.o mincore.o \
mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
- vmalloc.o pagewalk.o pgtable-generic.o
+ vmalloc.o pagewalk.o pgtable-generic.o \
+ process_vm_access.o

obj-y := filemap.o mempool.o oom_kill.o fadvise.o \
maccess.o page_alloc.o page-writeback.o \
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
new file mode 100644
index 0000000..e920aa3
--- /dev/null
+++ b/mm/process_vm_access.c
@@ -0,0 +1,496 @@
+/*
+ * linux/mm/process_vm_access.c
+ *
+ * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/mm.h>
+#include <linux/uio.h>
+#include <linux/sched.h>
+#include <linux/highmem.h>
+#include <linux/ptrace.h>
+#include <linux/slab.h>
+#include <linux/syscalls.h>
+
+#ifdef CONFIG_COMPAT
+#include <linux/compat.h>
+#endif
+
+/**
+ * process_vm_rw_pages - read/write pages from task specified
+ * @task: task to read/write from
+ * @mm: mm for task
+ * @process_pages: struct pages area that can store at least
+ * nr_pages_to_copy struct page pointers
+ * @pa: address of page in task to start copying from/to
+ * @start_offset: offset in page to start copying from/to
+ * @len: number of bytes to copy
+ * @lvec: iovec array specifying where to copy to/from
+ * @lvec_cnt: number of elements in iovec array
+ * @lvec_current: index in iovec array we are up to
+ * @lvec_offset: offset in bytes from current iovec iov_base we are up to
+ * @vm_write: 0 means copy from, 1 means copy to
+ * @nr_pages_to_copy: number of pages to copy
+ * @bytes_copied: returns number of bytes successfully copied
+ * Returns 0 on success, error code otherwise
+ */
+static int process_vm_rw_pages(struct task_struct *task,
+ struct mm_struct *mm,
+ struct page **process_pages,
+ unsigned long pa,
+ unsigned long start_offset,
+ unsigned long len,
+ const struct iovec *lvec,
+ unsigned long lvec_cnt,
+ unsigned long *lvec_current,
+ size_t *lvec_offset,
+ int vm_write,
+ unsigned int nr_pages_to_copy,
+ ssize_t *bytes_copied)
+{
+ int pages_pinned;
+ void *target_kaddr;
+ int pgs_copied = 0;
+ int j;
+ int ret;
+ ssize_t bytes_to_copy;
+ ssize_t rc = 0;
+
+ *bytes_copied = 0;
+
+ /* Get the pages we're interested in */
+ down_read(&mm->mmap_sem);
+ pages_pinned = get_user_pages(task, mm, pa,
+ nr_pages_to_copy,
+ vm_write, 0, process_pages, NULL);
+ up_read(&mm->mmap_sem);
+
+ if (pages_pinned != nr_pages_to_copy) {
+ rc = -EFAULT;
+ goto end;
+ }
+
+ /* Do the copy for each page */
+ for (pgs_copied = 0;
+ (pgs_copied < nr_pages_to_copy) && (*lvec_current < lvec_cnt);
+ pgs_copied++) {
+ /* Make sure we have a non zero length iovec */
+ while (*lvec_current < lvec_cnt
+ && lvec[*lvec_current].iov_len == 0)
+ (*lvec_current)++;
+ if (*lvec_current == lvec_cnt)
+ break;
+
+ /*
+ * Will copy smallest of:
+ * - bytes remaining in page
+ * - bytes remaining in destination iovec
+ */
+ bytes_to_copy = min_t(ssize_t, PAGE_SIZE - start_offset,
+ len - *bytes_copied);
+ bytes_to_copy = min_t(ssize_t, bytes_to_copy,
+ lvec[*lvec_current].iov_len
+ - *lvec_offset);
+
+ target_kaddr = kmap(process_pages[pgs_copied]) + start_offset;
+
+ if (vm_write)
+ ret = copy_from_user(target_kaddr,
+ lvec[*lvec_current].iov_base
+ + *lvec_offset,
+ bytes_to_copy);
+ else
+ ret = copy_to_user(lvec[*lvec_current].iov_base
+ + *lvec_offset,
+ target_kaddr, bytes_to_copy);
+ kunmap(process_pages[pgs_copied]);
+ if (ret) {
+ *bytes_copied += bytes_to_copy - ret;
+ pgs_copied++;
+ rc = -EFAULT;
+ goto end;
+ }
+ *bytes_copied += bytes_to_copy;
+ *lvec_offset += bytes_to_copy;
+ if (*lvec_offset == lvec[*lvec_current].iov_len) {
+ /*
+ * Need to copy remaining part of page into the
+ * next iovec if there are any bytes left in page
+ */
+ (*lvec_current)++;
+ *lvec_offset = 0;
+ start_offset = (start_offset + bytes_to_copy)
+ % PAGE_SIZE;
+ if (start_offset)
+ pgs_copied--;
+ } else {
+ start_offset = 0;
+ }
+ }
+
+end:
+ if (vm_write) {
+ for (j = 0; j < pages_pinned; j++) {
+ if (j < pgs_copied)
+ set_page_dirty_lock(process_pages[j]);
+ put_page(process_pages[j]);
+ }
+ } else {
+ for (j = 0; j < pages_pinned; j++)
+ put_page(process_pages[j]);
+ }
+
+ return rc;
+}
+
+/* Maximum number of pages kmalloc'd to hold struct page's during copy */
+#define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)
+
+/**
+ * process_vm_rw_single_vec - read/write pages from task specified
+ * @addr: start memory address of target process
+ * @len: size of area to copy to/from
+ * @lvec: iovec array specifying where to copy to/from locally
+ * @lvec_cnt: number of elements in iovec array
+ * @lvec_current: index in iovec array we are up to
+ * @lvec_offset: offset in bytes from current iovec iov_base we are up to
+ * @process_pages: struct pages area that can store at least
+ * nr_pages_to_copy struct page pointers
+ * @mm: mm for task
+ * @task: task to read/write from
+ * @vm_write: 0 means copy from, 1 means copy to
+ * @bytes_copied: returns number of bytes successfully copied
+ * Returns 0 on success or on failure error code
+ */
+static int process_vm_rw_single_vec(unsigned long addr,
+ unsigned long len,
+ const struct iovec *lvec,
+ unsigned long lvec_cnt,
+ unsigned long *lvec_current,
+ size_t *lvec_offset,
+ struct page **process_pages,
+ struct mm_struct *mm,
+ struct task_struct *task,
+ int vm_write,
+ ssize_t *bytes_copied)
+{
+ unsigned long pa = addr & PAGE_MASK;
+ unsigned long start_offset = addr - pa;
+ unsigned long nr_pages;
+ ssize_t bytes_copied_loop;
+ ssize_t rc = 0;
+ unsigned long nr_pages_copied = 0;
+ unsigned long nr_pages_to_copy;
+ unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
+ / sizeof(struct pages *);
+
+ *bytes_copied = 0;
+
+ /* Work out address and page range required */
+ if (len == 0)
+ return 0;
+ nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
+
+ while ((nr_pages_copied < nr_pages) && (*lvec_current < lvec_cnt)) {
+ nr_pages_to_copy = min(nr_pages - nr_pages_copied,
+ max_pages_per_loop);
+
+ rc = process_vm_rw_pages(task, mm, process_pages, pa,
+ start_offset, len,
+ lvec, lvec_cnt,
+ lvec_current, lvec_offset,
+ vm_write, nr_pages_to_copy,
+ &bytes_copied_loop);
+ start_offset = 0;
+ *bytes_copied += bytes_copied_loop;
+
+ if (rc < 0) {
+ return rc;
+ } else {
+ len -= bytes_copied_loop;
+ nr_pages_copied += nr_pages_to_copy;
+ pa += nr_pages_to_copy * PAGE_SIZE;
+ }
+ }
+
+ return rc;
+}
+
+/* Maximum number of entries for process pages array
+ which lives on stack */
+#define PVM_MAX_PP_ARRAY_COUNT 16
+
+/**
+ * process_vm_rw_core - core of reading/writing pages from task specified
+ * @pid: PID of process to read/write from/to
+ * @lvec: iovec array specifying where to copy to/from locally
+ * @liovcnt: size of lvec array
+ * @rvec: iovec array specifying where to copy to/from in the other process
+ * @riovcnt: size of rvec array
+ * @flags: currently unused
+ * @vm_write: 0 if reading from other process, 1 if writing to other process
+ * Returns the number of bytes read/written or error code. May
+ * return less bytes than expected if an error occurs during the copying
+ * process.
+ */
+static ssize_t process_vm_rw_core(pid_t pid, const struct iovec *lvec,
+ unsigned long liovcnt,
+ const struct iovec *rvec,
+ unsigned long riovcnt,
+ unsigned long flags, int vm_write)
+{
+ struct task_struct *task;
+ struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
+ struct page **process_pages = pp_stack;
+ struct mm_struct *mm;
+ unsigned long i;
+ ssize_t rc = 0;
+ ssize_t bytes_copied_loop;
+ ssize_t bytes_copied = 0;
+ unsigned long nr_pages = 0;
+ unsigned long nr_pages_iov;
+ unsigned long iov_l_curr_idx = 0;
+ size_t iov_l_curr_offset = 0;
+ ssize_t iov_len;
+
+ /*
+ * Work out how many pages of struct pages we're going to need
+ * when eventually calling get_user_pages
+ */
+ for (i = 0; i < riovcnt; i++) {
+ iov_len = rvec[i].iov_len;
+ if (iov_len > 0) {
+ nr_pages_iov = ((unsigned long)rvec[i].iov_base
+ + iov_len)
+ / PAGE_SIZE - (unsigned long)rvec[i].iov_base
+ / PAGE_SIZE + 1;
+ nr_pages = max(nr_pages, nr_pages_iov);
+ }
+ }
+
+ if (nr_pages == 0)
+ return 0;
+
+ if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
+ /* For reliability don't try to kmalloc more than
+ 2 pages worth */
+ process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
+ sizeof(struct pages *)*nr_pages),
+ GFP_KERNEL);
+
+ if (!process_pages)
+ return -ENOMEM;
+ }
+
+ /* Get process information */
+ rcu_read_lock();
+ task = find_task_by_vpid(pid);
+ if (task)
+ get_task_struct(task);
+ rcu_read_unlock();
+ if (!task) {
+ rc = -ESRCH;
+ goto free_proc_pages;
+ }
+
+ task_lock(task);
+ if (__ptrace_may_access(task, PTRACE_MODE_ATTACH)) {
+ task_unlock(task);
+ rc = -EPERM;
+ goto put_task_struct;
+ }
+ mm = task->mm;
+
+ if (!mm || (task->flags & PF_KTHREAD)) {
+ task_unlock(task);
+ rc = -EINVAL;
+ goto put_task_struct;
+ }
+
+ atomic_inc(&mm->mm_users);
+ task_unlock(task);
+
+ for (i = 0; i < riovcnt && iov_l_curr_idx < liovcnt; i++) {
+ rc = process_vm_rw_single_vec(
+ (unsigned long)rvec[i].iov_base, rvec[i].iov_len,
+ lvec, liovcnt, &iov_l_curr_idx, &iov_l_curr_offset,
+ process_pages, mm, task, vm_write, &bytes_copied_loop);
+ bytes_copied += bytes_copied_loop;
+ if (rc != 0) {
+ /* If we have managed to copy any data at all then
+ we return the number of bytes copied. Otherwise
+ we return the error code */
+ if (bytes_copied)
+ rc = bytes_copied;
+ goto put_mm;
+ }
+ }
+
+ rc = bytes_copied;
+put_mm:
+ mmput(mm);
+
+put_task_struct:
+ put_task_struct(task);
+
+free_proc_pages:
+ if (process_pages != pp_stack)
+ kfree(process_pages);
+ return rc;
+}
+
+/**
+ * process_vm_rw - check iovecs before calling core routine
+ * @pid: PID of process to read/write from/to
+ * @lvec: iovec array specifying where to copy to/from locally
+ * @liovcnt: size of lvec array
+ * @rvec: iovec array specifying where to copy to/from in the other process
+ * @riovcnt: size of rvec array
+ * @flags: currently unused
+ * @vm_write: 0 if reading from other process, 1 if writing to other process
+ * Returns the number of bytes read/written or error code. May
+ * return less bytes than expected if an error occurs during the copying
+ * process.
+ */
+static ssize_t process_vm_rw(pid_t pid,
+ const struct iovec __user *lvec,
+ unsigned long liovcnt,
+ const struct iovec __user *rvec,
+ unsigned long riovcnt,
+ unsigned long flags, int vm_write)
+{
+ struct iovec iovstack_l[UIO_FASTIOV];
+ struct iovec iovstack_r[UIO_FASTIOV];
+ struct iovec *iov_l = iovstack_l;
+ struct iovec *iov_r = iovstack_r;
+ ssize_t rc;
+
+ if (flags != 0)
+ return -EINVAL;
+
+ /* Check iovecs */
+ if (vm_write)
+ rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
+ iovstack_l, &iov_l, 1);
+ else
+ rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
+ iovstack_l, &iov_l, 1);
+ if (rc <= 0)
+ goto free_iovecs;
+
+ rc = rw_copy_check_uvector(READ, rvec, riovcnt, UIO_FASTIOV,
+ iovstack_r, &iov_r, 0);
+ if (rc <= 0)
+ goto free_iovecs;
+
+ rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
+ vm_write);
+
+free_iovecs:
+ if (iov_r != iovstack_r)
+ kfree(iov_r);
+ if (iov_l != iovstack_l)
+ kfree(iov_l);
+
+ return rc;
+}
+
+SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
+ unsigned long, liovcnt, const struct iovec __user *, rvec,
+ unsigned long, riovcnt, unsigned long, flags)
+{
+ return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
+}
+
+SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
+ const struct iovec __user *, lvec,
+ unsigned long, liovcnt, const struct iovec __user *, rvec,
+ unsigned long, riovcnt, unsigned long, flags)
+{
+ return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
+}
+
+#ifdef CONFIG_COMPAT
+
+asmlinkage ssize_t
+compat_process_vm_rw(compat_pid_t pid,
+ const struct compat_iovec __user *lvec,
+ unsigned long liovcnt,
+ const struct compat_iovec __user *rvec,
+ unsigned long riovcnt,
+ unsigned long flags, int vm_write)
+{
+ struct iovec iovstack_l[UIO_FASTIOV];
+ struct iovec iovstack_r[UIO_FASTIOV];
+ struct iovec *iov_l = iovstack_l;
+ struct iovec *iov_r = iovstack_r;
+ ssize_t rc = -EFAULT;
+
+ if (flags != 0)
+ return -EINVAL;
+
+ if (!access_ok(VERIFY_READ, lvec, liovcnt * sizeof(*lvec)))
+ goto out;
+
+ if (!access_ok(VERIFY_READ, rvec, riovcnt * sizeof(*rvec)))
+ goto out;
+
+ if (vm_write)
+ rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
+ UIO_FASTIOV, iovstack_l,
+ &iov_l, 1);
+ else
+ rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
+ UIO_FASTIOV, iovstack_l,
+ &iov_l, 1);
+ if (rc <= 0)
+ goto free_iovecs;
+ rc = compat_rw_copy_check_uvector(READ, rvec, riovcnt,
+ UIO_FASTIOV, iovstack_r,
+ &iov_r, 0);
+ if (rc <= 0)
+ goto free_iovecs;
+
+ rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
+ vm_write);
+
+free_iovecs:
+ if (iov_r != iovstack_r)
+ kfree(iov_r);
+ if (iov_l != iovstack_l)
+ kfree(iov_l);
+
+out:
+ return rc;
+}
+
+asmlinkage ssize_t
+compat_sys_process_vm_readv(compat_pid_t pid,
+ const struct compat_iovec __user *lvec,
+ unsigned long liovcnt,
+ const struct compat_iovec __user *rvec,
+ unsigned long riovcnt,
+ unsigned long flags)
+{
+ return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
+ riovcnt, flags, 0);
+}
+
+asmlinkage ssize_t
+compat_sys_process_vm_writev(compat_pid_t pid,
+ const struct compat_iovec __user *lvec,
+ unsigned long liovcnt,
+ const struct compat_iovec __user *rvec,
+ unsigned long riovcnt,
+ unsigned long flags)
+{
+ return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
+ riovcnt, flags, 1);
+}
+
+#endif
diff --git a/security/keys/compat.c b/security/keys/compat.c
index 338b510..4c48e13 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -38,7 +38,7 @@ long compat_keyctl_instantiate_key_iov(

ret = compat_rw_copy_check_uvector(WRITE, _payload_iov, ioc,
ARRAY_SIZE(iovstack),
- iovstack, &iov);
+ iovstack, &iov, 1);
if (ret < 0)
return ret;
if (ret == 0)
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index eca5191..0b3f5d7 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1065,7 +1065,7 @@ long keyctl_instantiate_key_iov(key_serial_t id,
goto no_payload;

ret = rw_copy_check_uvector(WRITE, _payload_iov, ioc,
- ARRAY_SIZE(iovstack), iovstack, &iov);
+ ARRAY_SIZE(iovstack), iovstack, &iov, 1);
if (ret < 0)
return ret;
if (ret == 0)


--
cyeoh@au.ibm.com


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