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| author | Jann Horn <jannh@google.com> | 2024-08-06 21:51:42 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2024-08-18 08:45:39 -0700 |
| commit | 3c0da3d163eb32f1f91891efaade027fa9b245b9 (patch) | |
| tree | 044d7125e167dff4b438d662533ac955d6dd067d /fs/fuse | |
| parent | c3f2d783a459980eafd24c5af94ccd56a615961f (diff) | |
| download | lwn-3c0da3d163eb32f1f91891efaade027fa9b245b9.tar.gz lwn-3c0da3d163eb32f1f91891efaade027fa9b245b9.zip | |
fuse: Initialize beyond-EOF page contents before setting uptodate
fuse_notify_store(), unlike fuse_do_readpage(), does not enable page
zeroing (because it can be used to change partial page contents).
So fuse_notify_store() must be more careful to fully initialize page
contents (including parts of the page that are beyond end-of-file)
before marking the page uptodate.
The current code can leave beyond-EOF page contents uninitialized, which
makes these uninitialized page contents visible to userspace via mmap().
This is an information leak, but only affects systems which do not
enable init-on-alloc (via CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y or the
corresponding kernel command line parameter).
Link: https://bugs.chromium.org/p/project-zero/issues/detail?id=2574
Cc: stable@kernel.org
Fixes: a1d75f258230 ("fuse: add store request")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/fuse')
| -rw-r--r-- | fs/fuse/dev.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 9eb191b5c4de..7146038b2fe7 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -1618,9 +1618,11 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size, this_num = min_t(unsigned, num, PAGE_SIZE - offset); err = fuse_copy_page(cs, &page, offset, this_num, 0); - if (!err && offset == 0 && - (this_num == PAGE_SIZE || file_size == end)) + if (!PageUptodate(page) && !err && offset == 0 && + (this_num == PAGE_SIZE || file_size == end)) { + zero_user_segment(page, this_num, PAGE_SIZE); SetPageUptodate(page); + } unlock_page(page); put_page(page); |