Commit:     8118a859dc7abd873193986c77a8d9bdb877adc8
Parent:     71409a498e96a421bdc20e7275ebc4fab8b14cdc
Author:     Miao Xie <[EMAIL PROTECTED]>
AuthorDate: Wed Nov 21 14:55:19 2007 -0800
Committer:  Greg Kroah-Hartman <[EMAIL PROTECTED]>
CommitDate: Wed Nov 28 13:53:53 2007 -0800

    sysfs: fix off-by-one error in fill_read_buffer()
    I found that there is a off-by-one problem in the following code.
    Version:    2.6.24-rc2
    File:               fs/sysfs/file.c:118-122
    Function:   fill_read_buffer
        count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);
        BUG_ON(count > (ssize_t)PAGE_SIZE);
    Because according to the specification of the sysfs and the implement of
    the show methods, the show methods return the number of bytes which would
    be generated for the given input, excluding the trailing null.So if the
    return value of the show methods equals PAGE_SIZE - 1, the buffer is full
    in fact.  And if the return value equals PAGE_SIZE, the resulting string
    was already truncated,or buffer overflow occurred.
    This patch fixes an off-by-one error in fill_read_buffer.
    Signed-off-by: Miao Xie <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Acked-by: Tejun Heo <[EMAIL PROTECTED]>
    Signed-off-by: Greg Kroah-Hartman <[EMAIL PROTECTED]>
 fs/sysfs/file.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 27d1785..4045bdc 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -119,7 +119,11 @@ static int fill_read_buffer(struct dentry * dentry, struct 
sysfs_buffer * buffer
-       BUG_ON(count > (ssize_t)PAGE_SIZE);
+       /*
+        * The code works fine with PAGE_SIZE return but it's likely to
+        * indicate truncated result or overflow in normal use cases.
+        */
+       BUG_ON(count >= (ssize_t)PAGE_SIZE);
        if (count >= 0) {
                buffer->needs_read_fill = 0;
                buffer->count = count;
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