3.2.51-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: yonghua zheng <younghua.zheng@xxxxxxxxx>
commit 8c8296223f3abb142be8fc31711b18a704c0e7d8 upstream.
Recently we met quite a lot of random kernel panic issues after enabling
CONFIG_PROC_PAGE_MONITOR. After debuggind we found this has something
to do with following bug in pagemap:
In struct pagemapread:
struct pagemapread {
int pos, len;
pagemap_entry_t *buffer;
bool v2;
};
pos is number of PM_ENTRY_BYTES in buffer, but len is the size of
buffer, it is a mistake to compare pos and len in add_page_map() for
checking buffer is full or not, and this can lead to buffer overflow and
random kernel panic issue.
Correct len to be total number of PM_ENTRY_BYTES in buffer.
[akpm@xxxxxxxxxxxxxxxxxxxx: document pagemapread.pos and .len units, fix PM_ENTRY_BYTES definition]
Signed-off-by: Yonghua Zheng <younghua.zheng@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2:
- Adjust context
- There is no pagemap_entry_t definition; keep using u64]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -604,7 +604,7 @@ const struct file_operations proc_clear_
};
struct pagemapread {
- int pos, len;
+ int pos, len; /* units: PM_ENTRY_BYTES, not bytes */
u64 *buffer;
};
@@ -792,8 +792,8 @@ static ssize_t pagemap_read(struct file
if (!count)
goto out_task;
- pm.len = PM_ENTRY_BYTES * (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
- pm.buffer = kmalloc(pm.len, GFP_TEMPORARY);
+ pm.len = (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
+ pm.buffer = kmalloc(pm.len * PM_ENTRY_BYTES, GFP_TEMPORARY);
ret = -ENOMEM;
if (!pm.buffer)
goto out_task;
--
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