5.4-stable review patch. If anyone has any objections, please let me know.
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From: Jan Kara jack@suse.cz
[ Upstream commit fde2497d2bc3a063d8af88b258dbadc86bd7b57c ]
When fat_encode_fh_nostale() encodes file handle without a parent it stores only first 10 bytes of the file handle. However the length of the file handle must be a multiple of 4 so the file handle is actually 12 bytes long and the last two bytes remain uninitialized. This is not great at we potentially leak uninitialized information with the handle to userspace. Properly initialize the full handle length.
Link: https://lkml.kernel.org/r/20240205122626.13701-1-jack@suse.cz Reported-by: syzbot+3ce5dea5b1539ff36769@syzkaller.appspotmail.com Fixes: ea3983ace6b7 ("fat: restructure export_operations") Signed-off-by: Jan Kara jack@suse.cz Acked-by: OGAWA Hirofumi hirofumi@mail.parknet.co.jp Cc: Amir Goldstein amir73il@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/fat/nfs.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/fs/fat/nfs.c b/fs/fat/nfs.c index af191371c3529..bab63eeaf9cbc 100644 --- a/fs/fat/nfs.c +++ b/fs/fat/nfs.c @@ -130,6 +130,12 @@ fat_encode_fh_nostale(struct inode *inode, __u32 *fh, int *lenp, fid->parent_i_gen = parent->i_generation; type = FILEID_FAT_WITH_PARENT; *lenp = FAT_FID_SIZE_WITH_PARENT; + } else { + /* + * We need to initialize this field because the fh is actually + * 12 bytes long + */ + fid->parent_i_pos_hi = 0; }
return type;