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authorDavid Howells <dhowells@redhat.com>2019-12-06 01:30:37 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-12-06 02:56:20 +0300
commit8f868d68d335a17923dffb6858f8e9b656424699 (patch)
tree6e96ca824b200a94156881a754be61f2d2fa0d95 /fs/pipe.c
parent8c7b8c34ae952cc062c12d7db9ee2f298c09dca4 (diff)
downloadlinux-8f868d68d335a17923dffb6858f8e9b656424699.tar.xz
pipe: Fix missing mask update after pipe_wait()
Fix pipe_write() to not cache the ring index mask and max_usage as their values are invalidated by calling pipe_wait() because the latter function drops the pipe lock, thereby allowing F_SETPIPE_SZ change them. Without this, pipe_write() may subsequently miscalculate the array indices and pipe fullness, leading to an oops like the following: BUG: KASAN: slab-out-of-bounds in pipe_write+0xc25/0xe10 fs/pipe.c:481 Write of size 8 at addr ffff8880771167a8 by task syz-executor.3/7987 ... CPU: 1 PID: 7987 Comm: syz-executor.3 Not tainted 5.4.0-rc2-syzkaller #0 ... Call Trace: pipe_write+0xc25/0xe10 fs/pipe.c:481 call_write_iter include/linux/fs.h:1895 [inline] new_sync_write+0x3fd/0x7e0 fs/read_write.c:483 __vfs_write+0x94/0x110 fs/read_write.c:496 vfs_write+0x18a/0x520 fs/read_write.c:558 ksys_write+0x105/0x220 fs/read_write.c:611 __do_sys_write fs/read_write.c:623 [inline] __se_sys_write fs/read_write.c:620 [inline] __x64_sys_write+0x6e/0xb0 fs/read_write.c:620 do_syscall_64+0xca/0x5d0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe This is not a problem for pipe_read() as the mask is recalculated on each pass of the loop, after pipe_wait() has been called. Fixes: 8cefc107ca54 ("pipe: Use head and tail pointers for the ring, not cursor and length") Reported-by: syzbot+838eb0878ffd51f27c41@syzkaller.appspotmail.com Signed-off-by: David Howells <dhowells@redhat.com> Cc: Eric Biggers <ebiggers@kernel.org> [ Changed it to use a temporary variable 'mask' to avoid long lines -Linus ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/pipe.c')
-rw-r--r--fs/pipe.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index 05330fac081f..70313af23b39 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -389,7 +389,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
{
struct file *filp = iocb->ki_filp;
struct pipe_inode_info *pipe = filp->private_data;
- unsigned int head, max_usage, mask;
+ unsigned int head;
ssize_t ret = 0;
int do_wakeup = 0;
size_t total_len = iov_iter_count(from);
@@ -408,12 +408,11 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
}
head = pipe->head;
- max_usage = pipe->max_usage;
- mask = pipe->ring_size - 1;
/* We try to merge small writes */
chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
if (!pipe_empty(head, pipe->tail) && chars != 0) {
+ unsigned int mask = pipe->ring_size - 1;
struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
int offset = buf->offset + buf->len;
@@ -443,7 +442,8 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
}
head = pipe->head;
- if (!pipe_full(head, pipe->tail, max_usage)) {
+ if (!pipe_full(head, pipe->tail, pipe->max_usage)) {
+ unsigned int mask = pipe->ring_size - 1;
struct pipe_buffer *buf = &pipe->bufs[head & mask];
struct page *page = pipe->tmp_page;
int copied;
@@ -465,7 +465,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
spin_lock_irq(&pipe->wait.lock);
head = pipe->head;
- if (pipe_full(head, pipe->tail, max_usage)) {
+ if (pipe_full(head, pipe->tail, pipe->max_usage)) {
spin_unlock_irq(&pipe->wait.lock);
continue;
}
@@ -510,7 +510,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
break;
}
- if (!pipe_full(head, pipe->tail, max_usage))
+ if (!pipe_full(head, pipe->tail, pipe->max_usage))
continue;
/* Wait for buffer space to become available. */