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btrfs: send: limit number of clones and allocated memory size

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The arg->clone_sources_count is u64 and can trigger a warning when a
huge value is passed from user space and a huge array is allocated.
Limit the allocated memory to 8MiB (can be increased if needed), which
in turn limits the number of clone sources to 8M / sizeof(struct
clone_root) = 8M / 40 = 209715.  Real world number of clones is from
tens to hundreds, so this is future proof.

Reported-by: syzbot+4376a9a073770c173269@syzkaller.appspotmail.com
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2023-01-24 20:32:10 +01:00
parent eadd7deca0
commit 33e17b3f5a
1 changed files with 3 additions and 3 deletions
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6
fs/btrfs/send.c
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@ -8072,10 +8072,10 @@ long btrfs_ioctl_send(struct inode *inode, struct btrfs_ioctl_send_args *arg)
/* /*
* Check that we don't overflow at later allocations, we request * Check that we don't overflow at later allocations, we request
* clone_sources_count + 1 items, and compare to unsigned long inside * clone_sources_count + 1 items, and compare to unsigned long inside
* access_ok. * access_ok. Also set an upper limit for allocation size so this can't
* easily exhaust memory. Max number of clone sources is about 200K.
*/ */
if (arg->clone_sources_count > if (arg->clone_sources_count > SZ_8M / sizeof(struct clone_root)) {
ULONG_MAX / sizeof(struct clone_root) - 1) {
ret = -EINVAL; ret = -EINVAL;
goto out; goto out;
} }