On Thu, Sep 16, 2021 at 01:34:24PM -0700, Eric Biggers wrote: > From: Eric Biggers <ebiggers@xxxxxxxxxx> > > If the file size is almost S64_MAX, the calculated number of Merkle tree > levels exceeds FS_VERITY_MAX_LEVELS, causing FS_IOC_ENABLE_VERITY to > fail. This is unintentional, since as the comment above the definition > of FS_VERITY_MAX_LEVELS states, it is enough for over U64_MAX bytes of > data using SHA-256 and 4K blocks. (Specifically, 4096*128**8 >= 2**64.) > > The bug is actually that when the number of blocks in the first level is > calculated from i_size, there is a signed integer overflow due to i_size > being signed. Fix this by treating i_size is unsigned. > > This was found by the new test "generic: test fs-verity EFBIG scenarios" > (https://lkml.kernel.org/r/b1d116cd4d0ea74b9cd86f349c672021e005a75c.1631558495.git.boris@xxxxxx). > > This didn't affect ext4 or f2fs since those have a smaller maximum file > size, but it did affect btrfs which allows files up to S64_MAX bytes. > > Reported-by: Boris Burkov <boris@xxxxxx> > Fixes: 3fda4c617e84 ("fs-verity: implement FS_IOC_ENABLE_VERITY ioctl") > Fixes: fd2d1acfcadf ("fs-verity: add the hook for file ->open()") > Cc: <stable@xxxxxxxxxxxxxxx> # v5.4+ > Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> Ah good catch! I'll update the test to not work around it. Reviewed-by: Boris Burkov <boris@xxxxxx> > --- > fs/verity/enable.c | 2 +- > fs/verity/open.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/verity/enable.c b/fs/verity/enable.c > index 77e159a0346b1..60a4372aa4d75 100644 > --- a/fs/verity/enable.c > +++ b/fs/verity/enable.c > @@ -177,7 +177,7 @@ static int build_merkle_tree(struct file *filp, > * (level 0) and ascending to the root node (level 'num_levels - 1'). > * Then at the end (level 'num_levels'), calculate the root hash. > */ > - blocks = (inode->i_size + params->block_size - 1) >> > + blocks = ((u64)inode->i_size + params->block_size - 1) >> > params->log_blocksize; > for (level = 0; level <= params->num_levels; level++) { > err = build_merkle_tree_level(filp, level, blocks, params, > diff --git a/fs/verity/open.c b/fs/verity/open.c > index 60ff8af7219fe..92df87f5fa388 100644 > --- a/fs/verity/open.c > +++ b/fs/verity/open.c > @@ -89,7 +89,7 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, > */ > > /* Compute number of levels and the number of blocks in each level */ > - blocks = (inode->i_size + params->block_size - 1) >> log_blocksize; > + blocks = ((u64)inode->i_size + params->block_size - 1) >> log_blocksize; > pr_debug("Data is %lld bytes (%llu blocks)\n", inode->i_size, blocks); > while (blocks > 1) { > if (params->num_levels >= FS_VERITY_MAX_LEVELS) { > -- > 2.33.0 >
