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ubifs: wbuf: Don't leak kernel memory to flash 

Write buffers use a kmalloc()'ed buffer, they can leak
up to seven bytes of kernel memory to flash if writes are not
aligned.
So use ubifs_pad() to fill these gaps with padding bytes.
This was never a problem while scanning because the scanner logic
manually aligns node lengths and skips over these gaps.

Cc: <stable@vger.kernel.org>
Fixes: 1e51764a3c ("UBIFS: add new flash file system")
Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Richard Weinberger 2020-11-16 22:05:30 +01:00
parent 619ea229e9
commit 20f1431160
1 changed files with 11 additions and 2 deletions
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13
fs/ubifs/io.c
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@ -319,7 +319,7 @@ void ubifs_pad(const struct ubifs_info *c, void *buf, int pad)
{
uint32_t crc;
ubifs_assert(c, pad >= 0 && !(pad & 7));
ubifs_assert(c, pad >= 0);
if (pad >= UBIFS_PAD_NODE_SZ) {
struct ubifs_ch *ch = buf;
@ -764,6 +764,10 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len)
* write-buffer.
*/
memcpy(wbuf->buf + wbuf->used, buf, len);
if (aligned_len > len) {
ubifs_assert(c, aligned_len - len < 8);
ubifs_pad(c, wbuf->buf + wbuf->used + len, aligned_len - len);
}
if (aligned_len == wbuf->avail) {
dbg_io("flush jhead %s wbuf to LEB %d:%d",
@ -856,13 +860,18 @@ int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len)
}
spin_lock(&wbuf->lock);
if (aligned_len)
if (aligned_len) {
/*
* And now we have what's left and what does not take whole
* max. write unit, so write it to the write-buffer and we are
* done.
*/
memcpy(wbuf->buf, buf + written, len);
if (aligned_len > len) {
ubifs_assert(c, aligned_len - len < 8);
ubifs_pad(c, wbuf->buf + len, aligned_len - len);
}
}
if (c->leb_size - wbuf->offs >= c->max_write_size)
wbuf->size = c->max_write_size;