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authorAmir Goldstein <amir73il@gmail.com>2022-08-16 16:53:17 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2022-08-16 16:59:54 +0200
commitd6da19c9cace63290ccfccb1fc35151ffefc0bec (patch)
tree00e66911e1e16675007d324b91572ab73adac346 /fs/exportfs/expfs.c
parentLinux 6.0-rc1 (diff)
downloadlinux-d6da19c9cace63290ccfccb1fc35151ffefc0bec.tar.xz
linux-d6da19c9cace63290ccfccb1fc35151ffefc0bec.zip
locks: fix TOCTOU race when granting write lease
Thread A trying to acquire a write lease checks the value of i_readcount and i_writecount in check_conflicting_open() to verify that its own fd is the only fd referencing the file. Thread B trying to open the file for read will call break_lease() in do_dentry_open() before incrementing i_readcount, which leaves a small window where thread A can acquire the write lease and then thread B completes the open of the file for read without breaking the write lease that was acquired by thread A. Fix this race by incrementing i_readcount before checking for existing leases, same as the case with i_writecount. Use a helper put_file_access() to decrement i_readcount or i_writecount in do_dentry_open() and __fput(). Fixes: 387e3746d01c ("locks: eliminate false positive conflicts for write lease") Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/exportfs/expfs.c')
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