From 8c8296223f3abb142be8fc31711b18a704c0e7d8 Mon Sep 17 00:00:00 2001 From: yonghua zheng Date: Tue, 13 Aug 2013 16:01:03 -0700 Subject: [PATCH] fs/proc/task_mmu.c: fix buffer overflow in add_page_map() 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@linux-foundation.org: document pagemapread.pos and .len units, fix PM_ENTRY_BYTES definition] Signed-off-by: Yonghua Zheng Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index a11720767abc..107d026f5d6e 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -868,7 +868,7 @@ typedef struct { } pagemap_entry_t; struct pagemapread { - int pos, len; + int pos, len; /* units: PM_ENTRY_BYTES, not bytes */ pagemap_entry_t *buffer; bool v2; }; @@ -876,7 +876,7 @@ struct pagemapread { #define PAGEMAP_WALK_SIZE (PMD_SIZE) #define PAGEMAP_WALK_MASK (PMD_MASK) -#define PM_ENTRY_BYTES sizeof(u64) +#define PM_ENTRY_BYTES sizeof(pagemap_entry_t) #define PM_STATUS_BITS 3 #define PM_STATUS_OFFSET (64 - PM_STATUS_BITS) #define PM_STATUS_MASK (((1LL << PM_STATUS_BITS) - 1) << PM_STATUS_OFFSET) @@ -1127,8 +1127,8 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, goto out_task; pm.v2 = soft_dirty_cleared; - 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; -- 2.20.1