diff options
| author | Jann Horn <jannh@google.com> | 2018-07-07 05:37:22 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-09-26 08:35:08 +0200 |
| commit | 1533250294cf5fe0b5ea3be4b58732b6d758fc69 (patch) | |
| tree | fef6b106584526ac26c0dc645d9c122dd7b92f65 | |
| parent | 20d6cff3fc059ac32d92fc737a8b9e80bb01ee4e (diff) | |
mtdchar: fix overflows in adjustment of `count`
[ Upstream commit 6c6bc9ea84d0008024606bf5ba10519e20d851bf ]
The first checks in mtdchar_read() and mtdchar_write() attempt to limit
`count` such that `*ppos + count <= mtd->size`. However, they ignore the
possibility of `*ppos > mtd->size`, allowing the calculation of `count` to
wrap around. `mtdchar_lseek()` prevents seeking beyond mtd->size, but the
pread/pwrite syscalls bypass this.
I haven't found any codepath on which this actually causes dangerous
behavior, but it seems like a sensible change anyway.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/mtd/mtdchar.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c index 6d19835b80a9..0d244dac1ccb 100644 --- a/drivers/mtd/mtdchar.c +++ b/drivers/mtd/mtdchar.c @@ -160,8 +160,12 @@ static ssize_t mtdchar_read(struct file *file, char __user *buf, size_t count, pr_debug("MTD_read\n"); - if (*ppos + count > mtd->size) - count = mtd->size - *ppos; + if (*ppos + count > mtd->size) { + if (*ppos < mtd->size) + count = mtd->size - *ppos; + else + count = 0; + } if (!count) return 0; @@ -246,7 +250,7 @@ static ssize_t mtdchar_write(struct file *file, const char __user *buf, size_t c pr_debug("MTD_write\n"); - if (*ppos == mtd->size) + if (*ppos >= mtd->size) return -ENOSPC; if (*ppos + count > mtd->size) |