From 9d81ba6d49a7457784f0b6a71046818b86ec7e44 Mon Sep 17 00:00:00 2001 From: Edward Adam Davis Date: Wed, 27 Aug 2025 09:45:55 +0800 Subject: [PATCH] fuse: Block access to folio overlimit syz reported a slab-out-of-bounds Write in fuse_dev_do_write. When the number of bytes to be retrieved is truncated to the upper limit by fc->max_pages and there is an offset, the oob is triggered. Add a loop termination condition to prevent overruns. Fixes: 3568a9569326 ("fuse: support large folios for retrieves") Reported-by: syzbot+2d215d165f9354b9c4ea@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=2d215d165f9354b9c4ea Tested-by: syzbot+2d215d165f9354b9c4ea@syzkaller.appspotmail.com Signed-off-by: Edward Adam Davis Reviewed-by: Joanne Koong Signed-off-by: Miklos Szeredi --- fs/fuse/dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index e80cd8f2c049f..5150aa25e64be 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -1893,7 +1893,7 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode, index = outarg->offset >> PAGE_SHIFT; - while (num) { + while (num && ap->num_folios < num_pages) { struct folio *folio; unsigned int folio_offset; unsigned int nr_bytes; -- 2.47.3