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authorLinus Torvalds <torvalds@linux-foundation.org>2021-02-20 21:15:00 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-02-20 21:15:00 -0800
commit3342ff2698e9720f4040cc458a2744b2b32f5c3a (patch)
treea767eb2e72cc0b154e33cdcc01dd7459eea47181 /drivers/tty
parent2c405d1ab8b3103df2df541aaacc2113dc6c9fac (diff)
tty: protect tty_write from odd low-level tty disciplines
Al root-caused a new warning from syzbot to the ttyprintk tty driver returning a write count larger than the data the tty layer actually gave it. Which confused the tty write code mightily, and with the new iov_iter based code, caused a WARNING in iov_iter_revert(). syzbot correctly bisected the source of the new warning to commit 9bb48c82aced ("tty: implement write_iter"), but the oddity goes back much further, it just didn't get caught by anything before. Reported-by: syzbot+3d2c27c2b7dc2a94814d@syzkaller.appspotmail.com Fixes: 9bb48c82aced ("tty: implement write_iter") Debugged-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/tty_io.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 816e709afa56..082da38762fc 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -962,11 +962,14 @@ static inline ssize_t do_tty_write(
if (ret <= 0)
break;
+ written += ret;
+ if (ret > size)
+ break;
+
/* FIXME! Have Al check this! */
if (ret != size)
iov_iter_revert(from, size-ret);
- written += ret;
count -= ret;
if (!count)
break;