4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jan Kara <jack@xxxxxxx> [ 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@xxxxxxx Reported-by: syzbot+3ce5dea5b1539ff36769@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: ea3983ace6b7 ("fat: restructure export_operations") Signed-off-by: Jan Kara <jack@xxxxxxx> Acked-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> Cc: Amir Goldstein <amir73il@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/fat/nfs.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/fat/nfs.c b/fs/fat/nfs.c index eb192656fba27..f442a8d2f114b 100644 --- a/fs/fat/nfs.c +++ b/fs/fat/nfs.c @@ -139,6 +139,12 @@ 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; -- 2.43.0
