The patch titled
vfs: introduce FMODE_NEG_OFFSET for allowing negative f_pos
has been added to the -mm tree. Its filename is
vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos.patch
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Subject: vfs: introduce FMODE_NEG_OFFSET for allowing negative f_pos
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Now, rw_verify_area() checsk f_pos is negative or not. And if negative,
returns -EINVAL.
But, some special files as /dev/(k)mem and /proc/<pid>/mem etc.. has
negative offsets. And we can't do any access via read/write to the
file(device).
So introduce FMODE_NEG_OFFSET to allow negative file offsets.
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/char/mem.c | 4 ++++
fs/proc/base.c | 2 ++
fs/read_write.c | 21 +++++++++++++++++++--
include/linux/fs.h | 3 +++
4 files changed, 28 insertions(+), 2 deletions(-)
diff -puN drivers/char/mem.c~vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos drivers/char/mem.c
--- a/drivers/char/mem.c~vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos
+++ a/drivers/char/mem.c
@@ -869,6 +869,10 @@ static int memory_open(struct inode *ino
if (dev->dev_info)
filp->f_mapping->backing_dev_info = dev->dev_info;
+ /* Is /dev/mem or /dev/kmem ? */
+ if (dev->dev_info == &directly_mappable_cdev_bdi)
+ filp->f_mode |= FMODE_NEG_OFFSET;
+
if (dev->fops->open)
return dev->fops->open(inode, filp);
diff -puN fs/proc/base.c~vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos fs/proc/base.c
--- a/fs/proc/base.c~vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos
+++ a/fs/proc/base.c
@@ -855,6 +855,8 @@ static const struct file_operations proc
static int mem_open(struct inode* inode, struct file* file)
{
file->private_data = (void*)((long)current->self_exec_id);
+ /* OK to pass negative loff_t, we can catch out-of-range */
+ file->f_mode |= FMODE_NEG_OFFSET;
return 0;
}
diff -puN fs/read_write.c~vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos fs/read_write.c
--- a/fs/read_write.c~vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos
+++ a/fs/read_write.c
@@ -205,6 +205,20 @@ bad:
}
#endif
+static int
+__negative_fpos_check(struct file *file, loff_t pos, size_t count)
+{
+ /*
+ * pos or pos+count is negative here, check overflow.
+ * too big "count" will be caught in rw_verify_area().
+ */
+ if ((pos < 0) && (pos + count < pos))
+ return -EOVERFLOW;
+ if (file->f_mode & FMODE_NEG_OFFSET)
+ return 0;
+ return -EINVAL;
+}
+
/*
* rw_verify_area doesn't like huge counts. We limit
* them to something that fits in "int" so that others
@@ -222,8 +236,11 @@ int rw_verify_area(int read_write, struc
if (unlikely((ssize_t) count < 0))
return retval;
pos = *ppos;
- if (unlikely((pos < 0) || (loff_t) (pos + count) < 0))
- return retval;
+ if (unlikely((pos < 0) || (loff_t) (pos + count) < 0)) {
+ retval = __negative_fpos_check(file, pos, count);
+ if (retval)
+ return retval;
+ }
if (unlikely(inode->i_flock && mandatory_lock(inode))) {
retval = locks_mandatory_area(
diff -puN include/linux/fs.h~vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos include/linux/fs.h
--- a/include/linux/fs.h~vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos
+++ a/include/linux/fs.h
@@ -90,6 +90,9 @@ struct inodes_stat_t {
/* File was opened by fanotify and shouldn't generate fanotify events */
#define FMODE_NONOTIFY ((__force fmode_t)0x1000000)
+/* File is huge (eg. /dev/kmem): treat loff_t as unsigned */
+#define FMODE_NEG_OFFSET ((__force fmode_t)0x2000)
+
/*
* The below are the various read and write types that we support. Some of
* them include behavioral modifiers that send information down to the
_
Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are
linux-next.patch
vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos.patch
mm-clean-up-mm_counter.patch
mm-avoid-false-sharing-of-mm_counter.patch
mm-avoid-false-sharing-of-mm_counter-checkpatch-fixes.patch
mm-count-swap-usage.patch
mm-count-swap-usage-checkpatch-fixes.patch
vmscan-get_scan_ratio-cleanup.patch
mm-restore-zone-all_unreclaimable-to-independence-word.patch
mm-restore-zone-all_unreclaimable-to-independence-word-fix.patch
mm-restore-zone-all_unreclaimable-to-independence-word-fix-2.patch
mm-migratec-kill-anon-local-variable-from-migrate_page_copy.patch
nodemaskh-remove-macro-any_online_node.patch
cgroup-introduce-cancel_attach.patch
cgroup-introduce-coalesce-css_get-and-css_put.patch
cgroups-revamp-subsys-array.patch
cgroups-subsystem-module-loading-interface.patch
cgroups-subsystem-module-loading-interface-fix.patch
cgroups-subsystem-module-unloading.patch
cgroups-net_cls-as-module.patch
cgroups-blkio-subsystem-as-module.patch
cgroups-clean-up-cgroup_pidlist_find-a-bit.patch
memcg-add-interface-to-move-charge-at-task-migration.patch
memcg-move-charges-of-anonymous-page.patch
memcg-move-charges-of-anonymous-page-cleanup.patch
memcg-improve-performance-in-moving-charge.patch
memcg-avoid-oom-during-moving-charge.patch
memcg-move-charges-of-anonymous-swap.patch
memcg-move-charges-of-anonymous-swap-fix.patch
memcg-improve-performance-in-moving-swap-charge.patch
memcg-improve-performance-in-moving-swap-charge-fix.patch
cgroup-implement-eventfd-based-generic-api-for-notifications.patch
cgroup-implement-eventfd-based-generic-api-for-notifications-kconfig-fix.patch
cgroup-implement-eventfd-based-generic-api-for-notifications-fixes.patch
memcg-extract-mem_group_usage-from-mem_cgroup_read.patch
memcg-rework-usage-of-stats-by-soft-limit.patch
memcg-implement-memory-thresholds.patch
memcg-implement-memory-thresholds-checkpatch-fixes.patch
memcg-implement-memory-thresholds-checkpatch-fixes-fix.patch
memcg-typo-in-comment-to-mem_cgroup_print_oom_info.patch
memcg-use-generic-percpu-instead-of-private-implementation.patch
sysctl-clean-up-vm-related-variable-declarations.patch
sysctl-clean-up-vm-related-variable-declarations-fix.patch
devmem-dont-allow-seek-to-last-page.patch
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