The patch titled
vfs: introduce FMODE_UNSIGNED_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_UNSIGNED_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_UNSIGNED_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
@@ -873,6 +873,10 @@ 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_UNSIGNED_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
@@ -773,6 +773,8 @@ 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_UNSIGNED_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
@@ -222,6 +222,20 @@ 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_UNSIGNED_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
@@ -239,8 +253,11 @@ 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 {
/* Expect random access pattern */
#define FMODE_RANDOM ((__force fmode_t)0x1000)
+/* File is huge (eg. /dev/kmem): treat loff_t as unsigned */
+#define FMODE_UNSIGNED_OFFSET ((__force fmode_t)0x2000)
+
/* File was opened by fanotify and shouldn't generate fanotify events */
/* File was opened by fanotify and shouldn't generate fanotify events */
#define FMODE_NONOTIFY ((__force fmode_t)0x1000000)
_
Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are
origin.patch
ipc-semc-bugfix-for-semop-not-reporting-successful-operation.patch
linux-next.patch
percpu-online-cpu-before-memory-failed-in-pcpu_alloc_pages.patch
vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos.patch
mm-rename-anon_vma_lock-to-vma_lock_anon_vma.patch
mm-change-direct-call-of-spin_lockanon_vma-lock-to-inline-function.patch
mm-track-the-root-oldest-anon_vma.patch
mm-always-lock-the-root-oldest-anon_vma.patch
mm-extend-ksm-refcounts-to-the-anon_vma-root.patch
mm-extend-ksm-refcounts-to-the-anon_vma-root-fix.patch
oom-check-pf_kthread-instead-of-mm-to-skip-kthreads.patch
oom-give-current-access-to-memory-reserves-if-it-has-been-killed.patch
oom-avoid-sending-exiting-tasks-a-sigkill.patch
oom-filter-tasks-not-sharing-the-same-cpuset.patch
oom-sacrifice-child-with-highest-badness-score-for-parent.patch
oom-select-task-from-tasklist-for-mempolicy-ooms.patch
oom-enable-oom-tasklist-dump-by-default.patch
oom-avoid-oom-killer-for-lowmem-allocations.patch
oom-extract-panic-helper-function.patch
oom-remove-special-handling-for-pagefault-ooms.patch
oom-move-sysctl-declarations-to-oomh.patch
oom-remove-unnecessary-code-and-cleanup.patch
mm-rename-try_set_zone_oom-to-try_set_zonelist_oom.patch
oom-remove-constraint-argument-from-select_bad_process-and-__out_of_memory.patch
oom-fold-__out_of_memory-into-out_of_memory.patch
mm-use-for_each_online_cpu-in-vmstat.patch
mempolicy-reduce-stack-size-of-migrate_pages.patch
mempolicy-reduce-stack-size-of-migrate_pages-fix.patch
vmscan-tracing-add-trace-events-for-kswapd-wakeup-sleeping-and-direct-reclaim.patch
vmscan-tracing-add-trace-events-for-lru-page-isolation.patch
vmscan-tracing-add-trace-event-when-a-page-is-written.patch
vmscan-tracing-add-a-postprocessing-script-for-reclaim-related-ftrace-events.patch
vmscan-kill-prev_priority-completely.patch
vmscan-simplify-shrink_inactive_list.patch
vmscan-remove-unnecessary-temporary-vars-in-do_try_to_free_pages.patch
vmscan-set-up-pagevec-as-late-as-possible-in-shrink_inactive_list.patch
vmscan-set-up-pagevec-as-late-as-possible-in-shrink_page_list.patch
vmscan-update-isolated-page-counters-outside-of-main-path-in-shrink_inactive_list.patch
oom-dont-try-to-kill-oom_unkillable-child.patch
oom-oom_kill_process-doesnt-select-kthread-child.patch
oom-make-oom_unkillable_task-helper-function.patch
oom-oom_kill_process-needs-to-check-that-p-is-unkillable.patch
oom-proc-pid-oom_score-treat-kernel-thread-honestly.patch
oom-kill-duplicate-oom_disable-check.patch
oom-move-oom_disable-check-from-oom_kill_task-to-out_of_memory.patch
oom-cleanup-has_intersects_mems_allowed.patch
oom-remove-child-mm-check-from-oom_kill_process.patch
oom-give-the-dying-task-a-higher-priority.patch
oom-multi-threaded-process-coredump-dont-make-deadlock.patch
oom-move-badness-declaration-into-oomh.patch
oom-move-badness-declaration-into-oomh-fix.patch
cgroups-save-space-for-the-terminator.patch
memcg-remove-experimental-from-swap-account-config.patch
memcg-clean-up-try_charge-main-loop-v2.patch
memcg-clean-up-waiting-move-acct-v2.patch
memcg-clean-up-waiting-move-acct-v2-fix.patch
memcg-remove-redundant-codes.patch
memcg-remove-mem-from-arg-of-charge_common.patch
memcg-use-find_lock_task_mm-in-memory-cgroups-oom.patch
memcg-avoid-css_get.patch
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